Starting the output failed. please check the log for details.

[Phnx8]

what I tried:
updating nvidia game driver to the latest one.
running obs as an administrator, neither solutions helped.
here is the log: https://obsproject.com/logs/fbG51kXlLvqmfWEc

 

[R1CH]

It looks like you downgraded OBS to a version that doesn't have the encoder you previously selected. Update to the latest OBS.