Is this what you are encountering?
If so download their new version, here: https://design.cricut.com/#/download
Whatever the problem happened to be must have been caused by something on their end. The new version fixed whatever was wrong.
There was something about Malware as well.
I find their claim about malware to be vague and dubious. Read about it if you wish (link below) but there is no malware on this Mac. If the problem they allege exists, it is more likely simply an expired certificate from an older macOS version.
https://help.cricut.com/hc/en-us/articles/4407201102743-Design-Space-for-Desktop-Blank-White-Screen-Mac-Computers
An expired certificate is not malware. Besides, that Certificate does not exist on the Mac on which I just tested it, yet I encountered the problem they are characterizing as "malware".
Do not install some sketchy "anti-malware" tool as the above article may suggest. It doesn't explicitly say to do that, but Cricut said they scanned affected systems with various anti-virus apps but were unable to detect any problems. No wonder, since there are no viruses that affect macOS.
"Design Space" seems to be a decent app, but you have to wonder about the competence of some developers.