Miscellaneous topics that do not fit into specific categories.
If your exported Quick Access Toolbar (QAT) customization does not import into Microsoft 365 applications and no error message appears, the issue may be related to a corrupted customization file, application settings, or a problem with your Microsoft 365 installation. Since the behavior occurs across multiple applications, different Microsoft 365 versions, and different accounts, it is less likely to be caused by a single user profile. Try creating a new QAT customization with only one or two commands, export it, and then attempt to import it into the same application to determine whether the original export file is corrupted. You should also ensure that Microsoft 365 is fully updated, run an Office Quick Repair or Online Repair, and verify that you have permission to access the folder containing the exported customization file. If the issue continues after these steps, it may indicate a broader issue with the Office installation or a software bug, in which case contacting Microsoft Support with the exported customization file and details of the troubleshooting you have already completed would be the next recommended step.
I hope these steps help you resolve the issue and successfully import your QAT customizations.