@ijevansdesign What kind of converter are you using to:
1. convert from a port on your mac to the connection on the beamer?
2. Extend the signal from your mac to the beamer?
3. Possibly decode a signal from an extension system to the beamer?
The issue you report (unavailble resolutions) sounds like part of your chain is not able to handle the bandwidth you are transmitting over a the cable/convertor setup you are using. Can you test the directly plugged in port and cable/convertor chain piece by piece with different convertors and cabling (the ones you know work)?