I updated to the latest version of nodebb using git pull and the buttons have come back. However, I noticed during the installation that the same error message occurred.
"The package nodebb-theme-vanilla does not satisfy its siblings' peerDependencies requirements!"
^ I noticed I got that message every time I tried to install a plugin, even after I've updated nodebb.
These are what I get when I entered the command you showed
└── email@example.com peer invalid
npm ERR! peer invalid: firstname.lastname@example.org /home/hanmai/mynodebb/node_modules/nodebb-theme-vanilla
npm ERR! not ok code 0