To verify, open any Office application (e.g., Word, Excel, etc), then select File > Account. If you run into problems accessing Office ProPlus, you should verify that you have properly installed Office ProPlus (rather than a non-subscription of Office). This support article provides information for troubleshooting specific errors presented to you, as well as general steps for diagnosing Office ProPlus problems. For example, you could run into issues with activation, licensing, or connectivity.
Although Microsoft 365 ProPlus is designed to be easy to install, activate, and use, problems may occasionally arise.