Have you verified if the error occured on ECP as well? What's your Exchange server CU version and did you install the security update?
If you have installed the SU, check this official document firstly: Repair failed installations of Exchange Cumulative and Security updates
Try reinstalling the security update from an elevated command prompt to solve this issue.
Since we don't have enough information currently, it will be hard to find what lead to this issue exactly, would you please check if any error recorded in application log through event viewer?
And you could also refer to the general troubleshooting steps introduced here, compare with your scenario and try the resolution: How to Fix HTTP ERROR 500 in ECP/EAC after Login
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
And for the OWA health error, check the official document here: Troubleshooting OWA Health Set
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