I know it's "just a popup" for most users but it's indicative of the quality of the application and its updates, which were questionable (and I'm being generous) already anyway.
TEMPORARY FIX - run at your own risk
Tested and working at: 5 primary schools, 1 large secondary
@wobert has provided an SQL script to apply this fix automatically
If you're as cowboy brave as I am and want to try this, please report back to confirm if it works or not
Here's a quick fix - you don't need anyone to log out of sims to apply this UNOFFICIAL workaround:
Make sure you have a backup! This isn't an official fix, there's a risk here that something will go wrong, or you'll do something wrong, and break sims, which is much worse than having an annoying popup!
On the sims server, open Microsoft SQL Server Manager and connect to the Sims server (you can find out what it is from 'C:\Program Files (x86)\SIMS\SIMS .net\connect.ini' on a workstation with Sims installed. Look for the 'ServerName=' line. eg: "ServerName=SimsServer.county.sch.uk\Sims2022")
On the left, expand Databases, Sims, Tables - note that your database name might not be "Sims" exactly
Find the 'db_annual_entitlement_service_details' table
Right click > Edit top 200 rows
On the 'date_last_checked' column, change the DAY in the date to be '20' instead of '22' (eg: "2025-05-22 07:00:00.000" becomes "2025-05-20 07:00:00.000") - btw @Boredguythis 7am is hardcoded and doesn't change which is why it worked prior to 7am this morning but started to fail after!)
Click into another field - this applies the change to the date_last_checked column you've just made
if someone logs into sims between step 5 & 7 you'll end up with a red icon on the field you edited, that's okay, it just means your change didn't write, you may need to repeat these two steps for this fix to apply)
Once you've clicked away from this (so the change applies to the DB), log into sims on the server or a client. The eligibility check will be redone and will allow you to access census stuff normally without a login poopup either... At least, in testing this is the result, though I suspect it will recur unless the Sims crew can actually fix this problem.