Hi MeProActive,

Let's try resorting your account's list. This way, we'll be able to identify why you're unable to assign classs by batch on some accounts.

Let me guide you with these steps:

1. Click the Lists menu.
2. Select Chart of Accounts.
3. On the Account drop-down, select Re-sort List.
4. Click OK.

Afterward, let's try assigning classes again.

Once done, you can filter, sort, or total reports by class. Here's an article for more information: Filter, Sort, or Total Reports by Class.

Let me know if there's anything that I can help. Keep safe!