LightBurn files won’t transmit to my computer

I can no longer send LightBurn files from my Imac to the Ruida controller on my Thunder Laser 60 watt. Every time I try to send the file I get the following messages: file transfer failed; settings could not be read from controller; there was a problem sending data to the laser. The machine may be busy or paused. I can send the same file from my MacBook Air and it works perfectly. I am using LightBurn version 1.2.01
on the Imac and the MacBook Air. I have attached some screen shots of the problem.