At Ease is not compatible with System 7 Pro. If you intend to run System 7 Pro, then you cannot run At Ease.
Compatibility Checker v7.1.1, which ships with System 7 Pro, attempts to move At Ease 2.0 (Work Group version) from the System Folder of the active startup disk, even if At Ease is turned on. It gives an error that there were issues moving At Ease, but doesn't explain how to fix it, and doesn't remove any other items from System Folder.
With At Ease 1.0, it does move At Ease Setup, along with all incompatible items. Then the computer cannot start up again, because At Ease is still the chosen startup application, but it is not present because Compatibility Checker has moved it.
If At Ease 1.0 was removed from the System folder while it was 'ON', then startup with Disk Tools, drag Finder from within your System Folder (on your hard disk) to the root level of the hard disk, then drag Finder back to System Folder. This resets the boot blocks back to normal. The Macintosh should now startup to the Finder, but At Ease will not be active.