I used all day trying to figure out why I could not use a modem through the modem API, after some experimentation I figured out that the peripheral.call() function worked, but if I tried to wrap a peripheral before using it it just failed with an error (something about the function was nil).
I tried this with a printer too and it was the same story, peripheral.call() is fine but wrapping is not.
I know this isn't the most detailed description, but hope it helps anyway...

Edit:
It also appears that the distance always returns nil when using the peripheral.call() and peripheral.getMethods() also always returns an empty table.

Thanks for the report! Really sorry you spent so long on this, this is a pretty embarrassing bug on my part.

Fixed in 8b1773d - will upload a new release.

No problem, I downgraded one version and then everything was fine, I'm just so happy that there is still active development on this mod👌😉