It is expected that you will solve problems on behalf of your customers. Your first steps should be to check service health for existing, documented problems. If that doesn't address the customer issue, then you can use your admin privileges to troubleshoot the software, settings, and configuration.
However, there are several categories of issues that you will need to hand off to Microsoft to fix: https://docs.microsoft.com/en-us/partner-center/escalate-problems-to-microsoft