I have had the same exact problem & I'll list the steps I did to take care of fixing it:

1. Create a new folder on your desktop or somewhere that you can access. Name is whatever you wish.
2. Find the 3 digit company identifier(letters or numbers). It's the ID column in EasyAcct.
3. Go to where your data is stored. Local Drive or Network Drive either one.
4. Open up your windows explorer(File Icon on most everyone's taskbar at the bottom) & locate the folder where your data is at. 
5. In the top right hand corner you should see a search box...type *.xxx-->where xxx is the 3 digit identifier from EasyAcct for the company that will not work. This will list only files that pertain to the company you're having probs with. Once the search is done & all files are on the screen press ctrl + A to select all, right click & select copy then paste them into the new folder you created in step 1.
6. Once you do this go into your EasyAcct program & click on restore. When you go into the restore window the current data path should change to c:/. Now hit the dropdown arrow to the right of the current data path. It's going to say no backup files found...this is perfectly fine(DON'T PANIC). Click the dropdown arrow again & it should bring up a browse window & and ask you to select a path. Find the backup folder created when you first installed the 2025 update(BACKUPCOMPANY24 IS THE NAME OF IT). Click on this folder & hit enter or ok & it should take you into a new current data path that is your data path followed by BACKUPCOMPANY24.
7. Once you're in that folder you should see the company that you're having problems with. If not you will have to call tech support at EasyAcct & speak to them. If you do see it click on the company & click restore above it. This should then bring up the data path to where the company sits and ask you if you would like to restore to that location. You're going to have to say yes in order to get the problem solved & get back to some kind of normal. After you do that, click on company selection & it should return you to the original screen where your data is located.
8. From here you will have to go into the company you were having probs with and let is redo the conversion to get it ready for 2025. Once it's done & you are able to go into the company then you are ready to copy the data back to the original folder that contained the data & you should be able to get into the company from that point forward. I will warn you...you will probably have to put  some of the data back in again as this is a flaw in the whole process. I have had some that have retained the info all the way up to the point of conversion & I have had some others that have had to redo a week or 2 of payroll because it restored back to a point before the conversion. You can take your chances, but I don't know of any other way to get back into a company once it says it is unable to access the data file. If EasyAcct wants to send out a fix, by all means, please do. I hope this info helps, at least some, and I'm sorry for it being so lengthy.