The issue I faced here was:
- I installed a new version of ruby
- I added that version to my .tool-versions file
- I tried to run the application and was faced with the error
No preset version installed for ...
I imagine others will face this issue with different plugins, but the answer for me was to reshim so that the exectuables were created for the Ruby version I wanted to use:
asdf reshim ruby 2.5.6
After that I was able to run ruby executables for Rbuy 2.5.6.