Go to the BP_MasterFarmingActor and make sure in its Class Defaults the Net Dormancy setting is set to Awake then compile and save and do the same thing in the BP_MasterPlant and BP_MasterPlanter.

In newer versions of Survival Game Kit V2 the save system has been changed and will require some addional code changes to make saving work correctly with the farming actor.

Go to the BP_SGKSaveGame and copy the video below, if you do not have the other TempSaveData variables here like shown in the video you are likely using an older version of SGKv2, the changes to the save system are included in the SGKv2 patch notes from version 2.3.10 linked (Here).

Next go to the BP_SaveSystem and select the node shown below and tick on the options shown in the image below.

Copy the image below, locations are at the tops of the screenshots.

Save all the changes, and delete any existing save games you might have made before these changes as those saves wont contain any of the farming actor save data. Now when you save your farming actors should save and load their save data.