Look up if there is any error information on the server, that could lead you to the source of the issue, and make sure you are creating the new module correctly (odoo docs).

Have you created the access rights (CSV), and have you added all the information into the "__init__.py" and config?

Verify if there are no conflicting module names.

Edit:

A few other things you can try, in case the error you are getting in the server is not clear:
Create a clean database and check if the error persists. If this solves the issue, the error might be caused by some inconsistent state of the database.
If not, something else is causing it.

The module might not be compatible with your version, or it requires any further configuration.

Providing further information regarding the module you tried to import, or details of the error can help us figure out what could be the issue.