Seeking help with Illustrator font error

I'm attempting to open and edit a .svg sent over to me by a colleague. Upon opening the file, I receive an error box containing "This document uses fonts or characters which are not available or are in a different format than originally specified" (I have attached the image). I've installed the font package in question (Montserrat) and confirmed with my colleague that it's the same one he uses.

Unfortunately, the error seems to also make a general mess of the .svg; I am unable to properly edit it.

Thanks in advance for help!