I found this problem when installing newest version.
Bundler could not find compatible versions for gem "mongoid":
In snapshot (Gemfile.lock):
mongoid (= 6.1.0)
In Gemfile:
mongoid (~> 6.1.0)
mongoid-autoinc (~> 6.0.0) was resolved to 6.0.0, which depends on
mongoid (~> 6.0.0.rc0)
Running 'bundle update' will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.
I found this problem when installing newest version.