This is a known error observed in our now unsupported Rockstor v3. We do have a temporary workaround to get you back up and running that we have described in the thread below:
If you choose to go that route, make sure to also add the important step described by @ArmyHill01:
That being said, I would recommend you to consider migrating to Rockstor v4 as this will bring you to an up-to-date base OS and an updated Rockstor version where many bugs have been fixed. We do have documentation on how to perform this migration: https://rockstor.com/docs/howtos/v3_to_v4.html
I hope this helps, but don’t hesitate to open a new thread if you have more question(s) or would like some clarification(s) on the migration process… Many users here have completed it and will be happy to answer your question(s).