problem setting up iMessage in older iMac
I have an 2013 imac running catalina (10.15.7). I need to get a link from a colleague through imessage. When I go to to imessage to set it up, it asks for my apple ID and password. I supply them, and receive this message: "An error occurred during activation. Try again."
I have reset my password several times and receive the same error message. How do I set up iMessage when my password seems to generate an error message, when it contain's the necessary material (number, cap, lower case, special character)