UPDATE May 25:
The Arduino Cloud developers have now restored support for uploading to 3rd party derivatives of the officially supported boards from Arduino Cloud Editor on ChromeOS machines.
So the workarounds I described in my prior answer are no longer required and you can now use these derivative boards with Cloud Editor by simply selecting the equivalent official board from the "Select a device type" dialog.
Original answer:
Arduino officially supports uploading to a specific list of official boards from Arduino Cloud Editor on ChromeOS machines: Boards compatible with the Cloud Editor - Cloud Editor on Chromebook
Up until recently, there was also incidental support for ChromeOS users to upload to 3rd party compatibles and derivatives of those official boards boards (such as your "Pitsco PRIZM Robotic Controller") that use a general purpose USB to serial bridge chip (e.g., FTDI FT232R, Silicon Labs CP2102, WCH CH340).
That incidental support for these 3rd party boards was lost during a recent rewrite of Cloud Editor.
At this time, I can suggest some possible solutions for affected users:
- Use Cloud Editor on a Linux, macOS or Windows machine (the issue is specific to ChromeOS machines).
- Use one of the officially supported Arduino boards (I understand this option is less reasonable in the case where the supported boards are not a drop-in hardware replacement, as is the case with @Ray Salemi's "PRIZM Robotic Controller", but wanted to mention it for the benefit of others who have a clone-ish derivative board).
The impact on ChromeOS users only emerged a matter of days before the time I write this answer so there is a chance the situation will evolve. If other options become known or available, I'll make an update as appropriate so stay tuned.