@ecx Hi there, thanks for your question. It sounds like you have branch versioning established for your underlying geodatabase. To take advantage of this, you would need to make use of the Branch Versioning option of the ArcGIS Portal Feature Service writer parameters. Once you check the box next to Branch Versioning, you should be able to see the Version Name parameter become active:
So long as the data has been configured according to Esri's documentation on Branch Versioning,, then you should be able to access the versions available for your data within the Version Name parameter.
Give this Branch Versioning parameter a try. If you still run into issues after testing this parameter out, let me know and we can take a closer look at things.