I have gotten multiple reports of the radio addon not loading because of the GMod CLIENT being outdated. This is the solution to that problem:

• Your game version is outdated as it says.
  
• Switch to none/live, x86-64, prerelease or dev branch.
  
• Verify your game files via steam.
  
• Any old or outdated version of GMod is not supported.
  
• The version check exists to mantain a higher addon quality.

For the SERVER version problems please read this, it is a different problem: https://psteamcommunity.yuanyoumao.com/workshop/filedetails/discussion/246756300/1700541698697801597/