One other person reported this yesterday, but prior to that other people had reported successful link ups, so I’m not sure what’s going on. 
Do you have other Matter devices successfully working with your V2 hub?
If so, check to make sure the aqara firmware is up to date, and take a quick glance through the following checklist…
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?
After that, you may need to open a support ticket. The first person you get will probably be a general Samsung employee working from a script and may not know much about smartthings, but persevere, and it should get escalated to a smartthings engineer who can take a look at it.
Adding an aqara m2 hub to a smartthings v2 hub via matter is definitely a supported integration, so it does sound like something may have broken. 