Hey,
Well since you've added it to a solution you acceptet using connection references. (Those make it easier to get the FLow running in another environment)
The new designer can't handle them for now.
To get it working you would need to identify where those connection references are and switch back to normal connections/recreate normale connections
If this solvede your porblem please accept it as solution so others can find it as well.
If it helped in any other way consider liking it so we can keep supporting eachother.