I am unable to import epics as a parent via csv. I created a simple example by exporting a minimal set of issues to csv and trying to re-import them.
Issue Type;Issue key;Issue id;Summary;Parent
Epic;TESTTENS-90;16361;Epic 1;
Task;TESTTENS-91;16362;Task 1;16361
Sub-task;TESTTENS-92;16363;Sub-task 1;16362
Sub-task;TESTTENS-93;16364;Sub-task 2;16362
The import config:

the error message i get:

2026-02-23 13:20:54,128 INFO - ------------------------------
2026-02-23 13:20:54,128 INFO - Importing: Work Items
2026-02-23 13:20:54,128 INFO - ------------------------------
2026-02-23 13:20:54,128 INFO - Only new items will be imported
2026-02-23 13:20:54,285 INFO - Importing work item: [externalId='16361', summary='Epic 1']
2026-02-23 13:20:55,360 WARN - Cannot add value [ [TESTTENS-106] ] to CustomField Epic Link in Work item with summary 'Task 1'. Probably value was in incorrect format
2026-02-23 13:20:55,365 INFO - Importing work item: [externalId='16362', summary='Task 1']
2026-02-23 13:20:56,084 INFO - Importing work item: [externalId='16363', summary='Sub-task 1']
2026-02-23 13:20:56,825 INFO - Importing work item: [externalId='16364', summary='Sub-task 2']
2026-02-23 13:20:57,623 INFO - 4 work items successfully created
2026-02-23 13:20:57,623 INFO - 0 out of 4 work items successfully updated
2026-02-23 13:20:57,628 INFO - ------------------------------
2026-02-23 13:20:57,628 INFO - Finished Importing : Work Items
2026-02-23 13:20:57,628 INFO - ------------------------------
2026-02-23 13:20:57,697 INFO - ------------------------------
2026-02-23 13:20:57,697 INFO - Importing: Work item
2026-02-23 13:20:57,697 INFO - ------------------------------
2026-02-23 13:20:57,697 INFO - Only new items will be imported
2026-02-23 13:20:57,706 INFO - Linking 'TESTTENS-108' and 'TESTTENS-107' as sub-task-link
2026-02-23 13:20:58,226 INFO - Created parent-child (sub-task) relationship between TESTTENS-108 and TESTTENS-107
2026-02-23 13:20:58,234 INFO - Linking 'TESTTENS-109' and 'TESTTENS-107' as sub-task-link
2026-02-23 13:20:58,696 INFO - Created parent-child (sub-task) relationship between TESTTENS-109 and TESTTENS-107
2026-02-23 13:20:58,702 INFO - ------------------------------
2026-02-23 13:20:58,702 INFO - Finished Importing : Work item
2026-02-23 13:20:58,702 INFO - ------------------------------
importing multiple issues with parent links (Epic-Task-Subtask) was no problem and an quick task using jira server a few years back.. now i can not do it at all....