At
Settings,
Output, tab
Recording you will find the
Recording Path. This is where recordings are saved, provided that it is a valid location, not write protected, enough diskspace etc.
At
Settings,
Advanced,
Recording:
File Formatting you'll find the pattern used for naming the files.
%CCYY-%MM-%DD %hh-%mm-%ss leads to i.e.
2022-01-17 08-41-58.mkv
If it does not contain any variables, i.e.
MyGreatRecording only, you can overwrite the same file over and over again (if overwrite is checked).
Could you please use Windows Explorer, go to
%APPDATA%\obs-studio\logs and provide the logfile of the OBS session of your recording.
https://obsproject.com/forum/threads/please-post-a-log-with-your-issue-heres-how.23074/