You are getting that error because the IDs of the Free-Space profiles you are trying to merge have special characters (periods, commas, etc.). Please carefully follow the instructions provided in the form:
Note that if the IDs have special characters, e.g. periods and commas, you will need to enter them like "Space:St. Stephen Church, Toledo, Ohio" instead of "Space:St._Stephen_Church%2C_Toledo%2C_Ohio"
You'll complete the merge with no issues.