Let's go through the documentation here since I see you are using the C:\ drive for this stuff...
First of all, delete the entire C:\UO folder and start over. Delete your UltimaOdyssey.zip file and download a fresh one because I fixed something today and another issue in the README that may have caused your issue.
drive.google.com
Then the instructions state to extract the UltimaOdyssey.zip onto the C:\ drive. This should then leave you with a C:\UO folder.
Go into C:\UO and run Odyssey.exe. Once you see a message like "CC Initialized...Cleanup: Detected XXX inaccessible items, removing.." then your server is up and running.
SERVER SETUP COMPLETE...NOW THE CLIENT...
Delete any clients you have except "ClassicUO.7z". If you do not have "ClassicUO.7z" go get it from here:
drive.google.com
Once you download it, extract it (you may need to get 7zip) into your C:\UO directory. When that is done, you should have a folder "C:\UO\ClassicUO".
Go into "C:\UO\ClassicUO" and run "ClassicUO.exe".
Log in as the admin account:
USERNAME: Wizard
PASSWORD: admin
If you get logged in and can run around, then your client is working.
While you are logged in, run the [buildworld command by typing it in the text chat line and pressing ENTER.
The server will rebuild/refresh around you and tell you when it is complete.
Once that is done, log out of the Wizard account.
Then you can log in with an account and password of your choice and play. DO NOT log in as the Wizard account and play.