when I try to sign in it says there is an error

Messages – Can’t log in. https://discussions.apple.com/thread/5261870?answerId=22814223022#22814223022

Messages – Can’t log in 2. https://discussions.apple.com/docs/DOC-11291

Messages - If you can‘t sign in to your iMessage account or FaceTime on your Mac. https://support.apple.com/en-us/HT204408

Message activation error. https://www.hawkdive.com/imessage-activation-error-occured-mac/

Have someone else attempt to sign in using their Apple ID. If they can successfully sign in and use Messages/FaceTime, it may be your Apple ID. Someone I know had this happen and I was able to sign in using my Apple ID. After a call to Apple Support and then being elevated to a tier 2 support person, it turned out it was a problem with their Apple ID. It took the software engineers 3-4 days to fix the problem. When calling Apple, make sure you tell them it is an Apple ID problem so you don't get charged.

You can also try signing in on another device/computer. There have been a couple of posts where people's device/computer was blocked. You will need to contact Apple for that problem also.

There is a contact link.

Apple ID - Official Apple Support. https://support.apple.com/apple-id

Contact Apple for help with Apple ID account security - Apple Support. https://support.apple.com/en-us/HT204169

Get Support https://getsupport.apple.com/. Work through the screens to get a chat option.

https://twitter.com/AppleSupport

Or fill out and submit iTunes Store - Contact Us - Official Apple Support https://support.apple.com/en-euro/itunes-contact

The form is for iTunes, but it will get passed to the ID Support section.

Where are you trying to sign in when you get the error? More information would help.