RubyMine require: "No such file to load" for a Gem

Hi RubyMine, JetBrains,

I'm a long time Python (with PyCharm) developer learning Ruby here so apologies if it's an easy question.

I'm using "RubyMine 2020.2.3 Build #RM-202.7660.39, built on October 8, 2020" evaluation at the moment. In a Debian 10 with "rvm" installed as suggested by RubyMine/IntelliJ documentation.

When I do "require 'mechanize'" (or other installed Gems) it works but RubyMine code editor says (when I press F2 or I go to the warning) "No such file to load" in the module.

(I've quickly tested with another package, 'wolfram', and it worked fine... is there anything special with 'mechanize'? Like https://youtrack.jetbrains.com/issue/RUBY-6626?)

Steps to reproduce:

• File -> New Project
• I create a new project (e.g. ruby-mine-test) and I leave selected "RVM: ruby-2.7.0". I don't create (but I've tried) "Use gemset"... . I click on "Create"
• Tools -> Bundler -> Init
• In the file "Gemfile" I write a new line: "gem 'mechanize'"
• Tools -> Bundle -> Install. No arguments. It seems all good: "Bundle complete! 1 Gemfile dependency, 15 gems now installed"
• Right click on the root of the new project -> New -> Ruby File/Class. I name it "ruby-mine-test.rb"
• I type "require 'mechanize'" (autocompletion works when I type "mec..." and I can select 'mechanize'
• I press "F2" and it goes to just before "'" in mechanize and it says "No such file to load"

Executing it works fine, the auto-completion if I typed "m = Mechanize." works (even without the require).

I've tried a few solutions from Google but no luck. Since it's a very simple example I'd like to know if I'm doing anything wrong or if I should double check anything in my system's installation.

Thank you very much for your information,

Carles