Going to somewhat ask and answer the issue myself in case it helps others in the future (including myself)
I have the NextCloud App installed on my Android Device and Auto Uploads stopped working and upon investigation it reported “Server in Maintenance Mode” however that was not the case. I verified by reviewing the /config/config.php file which confirmed the server was not in maintenance mode.
The Resolution was that there was an app that had been trying to synch the Calendar but my password had been changed. After X number of failed attempts the Account was Automatically locked and disabled requiring it to be reactivated by the Administrator.
It happened to me once before and I had forgotten that was the cause.
Did you recently perform a system upgrade or other maintenance? Since you gave no details it is not possible to advise further. Good luck!
Check your Nextcloud system logs or go back through steps that led to this. Probably also want to share some of your setup details so we can understand what you are actually using for hosting your nc.
There was no Server Upgrade. Everything had been normal when the client stopped Auto Uploading new files and and the error message showed Server in Maintenance Mode.
As my original post suggested… I asked and answered the issue so that others may be able to reference it if needed.
The issue was that I had changed my password, but I have another app synching the calendar but the password was wrong, so NextCloud disabled the account after repeated failed login attempts. The Android App then displayed the error that the Server was in Maintenance Mode (which was not accurate). The account was in fact disabled. Once the account was re enabled (and deleted the other app), the issue was resolved.
Next Cloud in theory should really provide a correct error message to the user when the account was disabled due to too many incorrect login attempts, but instead shows as Server in Maintenance Mode… which in this case it was not, and I had already reviewed other posts about checking the config file etc…
Issue can be marked as Solved (although I cannot find where to do that)… its more to help others who may encounter the same error.