Can you please give the exact error?

Also, have you updated your graphics driver? Upgrade your graphics drivers to use hardware acceleration and WebGL

"The browser could not generate enough memory for the WebGL content. If you are the developer of this content, try allocating less memory to your WebGL build in the WebGL player settings."

It sounds like an issue with the website. Perhaps you should contact them with that error?

Nope, site works great on other browsers. Problem started with last Mozilla update.....

FYI, WEB gl error is a adobe error not a FF error. I search and came up with this result.

https://adobespark.zendesk.com/hc/en-us/articles/115000356593-I-am-getting-a-WebGL-error-message-

This can happen if the memory is too much fragmented and Firefox isn't able to allocate a contiguous block of memory that is large enough to run the game. You can try to close and restart Firefox to start with a fresh memory allocation and do not do anything apart from running the game. You can also check if it helps to reboot the computer and load as less programs as possible.