Please find below the detailed log, the message does not gives any specific error.
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2020-07-17 19:37:53,060 INFO - Import started by admin using com.atlassian.jira.plugins.importer.imports.csv.CsvDataBean
2020-07-17 19:37:53,309 INFO - ------------------------------
2020-07-17 19:37:53,310 INFO - Importing: Users
2020-07-17 19:37:53,310 INFO - ------------------------------
2020-07-17 19:37:53,310 INFO - Only new items will be imported
2020-07-17 19:37:53,317 INFO - 1 users associated with import. All of them imported as inactive, this can be changed after import in User Access step.
2020-07-17 19:37:53,317 INFO - ------------------------------
2020-07-17 19:37:53,317 INFO - Finished Importing : Users
2020-07-17 19:37:53,317 INFO - ------------------------------
2020-07-17 19:37:53,317 INFO - 0 users successfully created.
2020-07-17 19:37:53,322 INFO - Retrieving projects...
2020-07-17 19:37:53,338 INFO - Project ExternalProject{id='null', key='ISP', externalName='null', name='Isbank Prod', type='null', template='null'} exists and found correctly.
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - Importing: Versions
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - Only new items will be imported
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - Finished Importing : Versions
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - Importing: Components
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - Only new items will be imported
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,346 INFO - Finished Importing : Components
2020-07-17 19:37:53,346 INFO - ------------------------------
2020-07-17 19:37:53,353 INFO - Retrieving custom fields...
2020-07-17 19:37:53,360 INFO - ------------------------------
2020-07-17 19:37:53,360 INFO - Importing: Issues
2020-07-17 19:37:53,360 INFO - ------------------------------
2020-07-17 19:37:53,360 INFO - Only new items will be imported
2020-07-17 19:37:53,372 INFO - Importing issue: [externalId='autoid-1442210068879754273', summary='Adres Defteri Temel Niteliklerin Güncellenmesi']
2020-07-17 19:37:53,430 ERROR - Error importing issue [externalId='autoid-1442210068879754273', summary='Adres Defteri Temel Niteliklerin Güncellenmesi']: Unable to create issue: Adres Defteri Temel Niteliklerin Güncellenmesi
2020-07-17 19:37:53,442 INFO - 0 out of 1 issues successfully created
2020-07-17 19:37:53,447 INFO - ------------------------------
2020-07-17 19:37:53,447 INFO - Finished Importing : Issues
2020-07-17 19:37:53,447 INFO - ------------------------------
2020-07-17 19:37:53,453 INFO - ------------------------------
2020-07-17 19:37:53,453 INFO - Importing: Issue Links & Subtasks
2020-07-17 19:37:53,453 INFO - ------------------------------
2020-07-17 19:37:53,453 INFO - Only new items will be imported
2020-07-17 19:37:53,459 INFO - ------------------------------
2020-07-17 19:37:53,459 INFO - Finished Importing : Issue Links & Subtasks
2020-07-17 19:37:53,459 INFO - ------------------------------