diff --git a/CHANGELOG.md b/CHANGELOG.md
index 286040a34b..72bc376563 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -136,6 +136,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed `CHANGELOG` entry for issue ([#103](https://github.com/ie3-institute/simona/issues/103)) [#941](https://github.com/ie3-institute/simona/issues/941)
 - Fix grammar and spelling in docs and comments [#1022](https://github.com/ie3-institute/simona/issues/1022)
 - Fix some minor issues and findings from inspections [#1019](https://github.com/ie3-institute/simona/issues/1019)
+- Fix initialisation freezing on empty primary data [#981](https://github.com/ie3-institute/simona/issues/981)
 
 ## [3.0.0] - 2023-08-07
 
diff --git a/src/main/scala/edu/ie3/simona/agent/participant/ParticipantAgentFundamentals.scala b/src/main/scala/edu/ie3/simona/agent/participant/ParticipantAgentFundamentals.scala
index efb4150814..927007bb47 100644
--- a/src/main/scala/edu/ie3/simona/agent/participant/ParticipantAgentFundamentals.scala
+++ b/src/main/scala/edu/ie3/simona/agent/participant/ParticipantAgentFundamentals.scala
@@ -139,9 +139,8 @@ protected trait ParticipantAgentFundamentals[
 
     /* Confirm final initialization */
     releaseTick()
-    senderToMaybeTick._2.foreach { tick =>
-      scheduler ! Completion(self.toTyped, Some(tick))
-    }
+    scheduler ! Completion(self.toTyped, senderToMaybeTick._2)
+
     goto(Idle) using stateData
   }
 
diff --git a/src/main/scala/edu/ie3/simona/service/primary/PrimaryServiceWorker.scala b/src/main/scala/edu/ie3/simona/service/primary/PrimaryServiceWorker.scala
index bd09c0b81b..b20fdd834c 100644
--- a/src/main/scala/edu/ie3/simona/service/primary/PrimaryServiceWorker.scala
+++ b/src/main/scala/edu/ie3/simona/service/primary/PrimaryServiceWorker.scala
@@ -20,6 +20,7 @@ import edu.ie3.simona.agent.participant.data.Data.PrimaryData.RichValue
 import edu.ie3.simona.config.SimonaConfig.Simona.Input.Primary.SqlParams
 import edu.ie3.simona.exceptions.InitializationException
 import edu.ie3.simona.exceptions.WeatherServiceException.InvalidRegistrationRequestException
+import edu.ie3.simona.exceptions.agent.ServiceRegistrationException
 import edu.ie3.simona.ontology.messages.services.ServiceMessage
 import edu.ie3.simona.ontology.messages.services.ServiceMessage.RegistrationResponseMessage.RegistrationSuccessfulMessage
 import edu.ie3.simona.service.ServiceStateData.{
@@ -131,32 +132,47 @@ final case class PrimaryServiceWorker[V <: Value](
             s"Provided init data '${unsupported.getClass.getSimpleName}' for primary service are invalid!"
           )
         )
-    }).map { case (source, simulationStart) =>
+    }).flatMap { case (source, simulationStart) =>
       implicit val startDateTime: ZonedDateTime = simulationStart
 
       val (maybeNextTick, furtherActivationTicks) = SortedDistinctSeq(
         // Note: The whole data set is used here, which might be inefficient depending on the source implementation.
         source.getTimeSeries.getEntries.asScala
-          .filter { timeBasedValue =>
-            val dateTime = timeBasedValue.getTime
-            dateTime.isEqual(simulationStart) || dateTime.isAfter(
-              simulationStart
-            )
-          }
           .map(timeBasedValue => timeBasedValue.getTime.toTick)
+          .filter(_ >= 0L)
           .toSeq
           .sorted
       ).pop
 
-      /* Set up the state data and determine the next activation tick. */
-      val initializedStateData =
-        PrimaryServiceInitializedStateData(
-          maybeNextTick,
-          furtherActivationTicks,
-          simulationStart,
-          source,
-        )
-      (initializedStateData, maybeNextTick)
+      (maybeNextTick, furtherActivationTicks) match {
+        case (Some(tick), furtherActivationTicks) if tick == 0L =>
+          /* Set up the state data and determine the next activation tick. */
+          val initializedStateData =
+            PrimaryServiceInitializedStateData(
+              maybeNextTick,
+              furtherActivationTicks,
+              simulationStart,
+              source,
+            )
+
+          Success(initializedStateData, maybeNextTick)
+
+        case (Some(tick), _) if tick > 0L =>
+          /* The start of the data needs to be at the first tick of the simulation. */
+          Failure(
+            new ServiceRegistrationException(
+              s"The data for the timeseries '${source.getTimeSeries.getUuid}' starts after the start of this simulation (tick: $tick)! This is not allowed!"
+            )
+          )
+
+        case _ =>
+          /* No data for the simulation. */
+          Failure(
+            new ServiceRegistrationException(
+              s"No appropriate data found within simulation time range in timeseries '${source.getTimeSeries.getUuid}'!"
+            )
+          )
+      }
     }
   }
 
diff --git a/src/test/scala/edu/ie3/simona/service/primary/PrimaryServiceWorkerSpec.scala b/src/test/scala/edu/ie3/simona/service/primary/PrimaryServiceWorkerSpec.scala
index db7e9abdea..c08f189b79 100644
--- a/src/test/scala/edu/ie3/simona/service/primary/PrimaryServiceWorkerSpec.scala
+++ b/src/test/scala/edu/ie3/simona/service/primary/PrimaryServiceWorkerSpec.scala
@@ -105,6 +105,32 @@ class PrimaryServiceWorkerSpec
       }
     }
 
+    "fail to init, if time series ends with delay before simulation start" in {
+      val initData = validInitData.copy(
+        simulationStart = validInitData.simulationStart.plusHours(1)
+      )
+
+      service.init(initData) match {
+        case Failure(exception) =>
+          exception.getMessage shouldBe "No appropriate data found within simulation time range in timeseries '9185b8c1-86ba-4a16-8dea-5ac898e8caa5'!"
+        case Success(_) =>
+          fail("Initialisation with unsupported init data is meant to fail.")
+      }
+    }
+
+    "fail to init, if time series starts with delay after simulation start" in {
+      val initData = validInitData.copy(
+        simulationStart = validInitData.simulationStart.minusHours(1)
+      )
+
+      service.init(initData) match {
+        case Failure(exception) =>
+          exception.getMessage shouldBe "The data for the timeseries '9185b8c1-86ba-4a16-8dea-5ac898e8caa5' starts after the start of this simulation (tick: 3600)! This is not allowed!"
+        case Success(_) =>
+          fail("Initialisation with unsupported init data is meant to fail.")
+      }
+    }
+
     "fail, if pointed to the wrong file" in {
       // time series exists, but is malformed
       val tsUuid = UUID.fromString("3fbfaa97-cff4-46d4-95ba-a95665e87c27")