Error with byebug when running 'bundle exec rspec'

All of a sudden when I run ‘bundle exec rspec’ i get:

~/3b6a1428-my_name-rspec-2 (master)$ bundle exec rspec
Could not find byebug-9.0.6 in any of the sources
Run `bundle install` to install missing gems.

I ran ‘bundle install’ (again) and it says:

~/3b6a1428-my_name-rspec-2 (master)$ bundle install
Using byebug 9.0.6
Using diff-lcs 1.3
Using rspec-support 3.2.2
Using bundler 1.14.6
Using rspec-core 3.2.3
Using rspec-expectations 3.2.1
Using rspec-mocks 3.2.1
Using rspec 3.2.0
Bundle complete! 2 Gemfile dependencies, 8 gems now installed.
Use `bundle show [gemname]` to see where a bundled gem is installed.

but I still get the same error after running ‘bundle exec rspec’

Please note, I have already forked and completed RSPEC Practice problems 1 with no problems (and used byebug), and am halfway through the second set of problems when all of a sudden this happened?! What went wrong and how do I fix it??