Hey @psmcd67,
I've tried to reproduce this issue locally with latest version of The Events Calendar (4.0.4) but it was working fine for me. Can you please retest with the latest version? In case the error is still present, Can you look for the error description in the server logs? Also can you please follow the steps described in our Testing for conflicts guide? This way we can see if this is a conflict with other installed plugins.
Best,
Nico