MongoDB/Mongoose challenges

Tell us what’s happening:
I managed to pass the first two, but none past that having tried several. Have pasted in the hint solutions and still no. When I go back to the first challenge, it will then fail the last test (i.e. not connected to DB), having passed that previously. I can then get it to work again by editing the code to what it was previously (e.g. deleting and replacing a semi-colon). It will then re-pass, but re-submitting the test a few more times will eventually lead to a fail again (without changing anything in the code or at all).

I’m assuming this is related to failing the subsequent tests.

Glitch continually provides a UnhandledPromiseRejectionWarning and a related DeprecationWarning, with links back to the server.js file.

Your code so far
Copied from hint solutions (replacing Mongo URL as needed).

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.163 Safari/537.36.

Challenge: undefined

Link to the challenge: