OWA sign in error: Error System.IO.FileNotFoundException

Question

Able to get to webmail sign in page but can't sign into OWA: -Error System.IO.FileNotFoundException

Answer 1

Hi Keith Hotchkiss

Some notes that you can track in your case.

• Some security updates can produce this error https://learn.microsoft.com/en-us/exchange/troubleshoot/client-connectivity/owa-stops-working-after-update
• Please read this article about missing DLL's https://stackoverflow.com/questions/39476355/getting-unhandled-exception-error-system-io-filenotfoundexception

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Answer 2

the exchange server is working now. i checked the version on all of them & the 1 that was not working had the old version. i re-installed .39 hotfix and the exchange server has been working since. the .39 hotfix update had been installed 2 months ago & worked fine after. the folder for .39 showed in the program files list but the powershell cmd to get the running version showed the previous version. hopefully this may help someone else.