Hi @Julie M
I'm glad to hear you solve the problem ,if you have any issue about SharePoint, you are welcome to raise a ticket in this forum.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.". and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[Unable to access Sharepoint App store]
Issue Symptom:
I have Global Admin rights on my tenant but Unable to open the Sharepoint App store to test some customization.
Someone please help on this?
Error when i access the Sharepoint admin portal --> More Features --> APP --> Open
Current status:
Its working now, the cause of this issue is that account was not part of the app catalog site.
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