As a stop-gap measure, you might have to back out the latest Windows update, though I'm almost afraid to ask ...
Which version of Windows are you using? If it is earlier than Windows 10, then someone has meddled with your program OR you have had a device failure. If it is Win10 or Win11, you could have had a Windows Update that changed something behind the scenes.
Open the Windows Settings and find the Windows Update screen. Somewhere on that screen you should be able to find the Update History, which would tell you the most recent updates. If the dates of the most recent updates are on or just before the time that the program failure occurred, it might be possible to roll back the updates to see if that fixes the problem.
However, if you are on older versions of Windows and of Office, they are out of support and you probably would not be able to get ANY help from Microsoft for less than several hundred dollars.
I remember when your site first came on board. You folks are actually several persons sharing the same account. I also recall that you folks are operating with a very limited budgets. I have to say this is a problem that has been coming for a long time. Eventually you are going to have to upgrade because Ac2003 is 23 years out of date. If you are using a version of Windows that is still supported, you WILL eventually run into a Windows patch that will - probably for security reasons - shut down the things that Ac2003 tries to do. That has been the trend over the years - having Access get tighter and tighter on security issues.
As to your problem, I would suggest this as a POSSIBLE (but not guaranteed) fix:
1. Make a copy of the database in question as a backup. When you make this copy, nobody else can have the DB open. Make the copy using Windows Explorer rather than using the Access ability to make a backup copy. Move that copy to a safe place in case the next step fails.
2. Perform a compact and repair (C&R) operation on the DB. If the DB got very mildly corrupted, the problem you describe COULD happen, thought I would have expected other issues, too. Once you do the C&R, see if it works better. If it works, great. If it doesn't, then some other solution will be required.