Plugin Roundcube Calendar

[ru_matrix]

I install the calendar plugin, after which I can't open the messages, what's the reason, please help? HTTP ERROR 500 

[ru_matrix]

I'm a beginner, nobody helped, and I don't need it, I guessed it myself, I help someone who will also be ignored:
1. Install the composer https://sabre.io/dav/install/
2. Install Git https://git-scm.com/downloads
3. In the GIT Bash Here:
                                   $ composer require sabre/vobject "^ 3.3"
                                   $ composer update sabre/vobject