If it's a fresh install and you have never used OBS Studio on this computer before, or if you don't mind losing your scenes and settings, you could try deleting all of the OBS Studio settings to force it to go back to default. If you want to do that, uninstall OBS Studio, delete "%AppData%\obs-studio", restart your computer, then reinstall OBS Studio.
If you don't want to lose all of your settings, you can try to delete just the profile settings file ("%AppData%\obs-studio\basic\<profilename>.ini" and see if OBS Studio will regenerate the file on restart. You will still lose some settings data this way.
If you
really want to minimize your data loss, and you're comfortable manually editing OBS settings files, then you can try to manually edit your profile settings file ("%AppData%\obs-studio\basic\<profilename>.ini"). In it, you should see two sections labeled "[Output]" and "[SimpleOutput]". Try deleting those sections, and OBS should select default values the next time it loads the profile. If that doesn't work, try pasting this in place of those sections:
Code:
[Output]
Mode=Simple
[SimpleOutput]
FilePath=C:\\Temp\\videos
RecFormat=flv
UseAdvanced=false
RecQuality=Stream
VBitrate=2500
EnforceBitrate=true
Preset=veryfast
RecEncoder=x264
You'll still lose whatever settings those had previously been.
Let us know what you decide to do and how it works out. Let us know if you still have issues after that.