iMessage failed on Hard Disk transfer to different MacBook

I transferred the Solid State Drive to a similar PC and loaded the system without incident, but iMessage does not work.

There seems to be a problem connecting to iCloud or Contacts, since if I create  New text message, typing into the To: field does not bring up Intellisense. By this I mean, it does not mater what I type, not contacts pop up. If I try and paste a phone number, it disappears.

What must I do to get it working again on this other machine?

newbiewebSr. Software EngineerAsked:
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You're listing Apple topics, but then asking about a PC?  Is this a Mac or Microsoft Windows PC?  I'll assume a Mac based on the other context.

How did you transfer the drive?  Did you just pull it out of the old Mac and place it in the new one?
How did you connect to iCloud?  Have you reloaded the account?
newbiewebSr. Software EngineerAuthor Commented:
This is a Mac. I moved the HD to the new PC and it works perfectly, except for iMessage.

I think I need to add the account again, but do not see how.

"Add Account..." I ran a test to set up a Google Account but got the attached error...

Proxy Error
Please don't call a Mac a PC, as that confuses matters when you're talking to a tech.  Technically, yes, it is a Personal Computer also, but you need to keep the labels correct when you refer to them or people will get confused.

This is because your network interface changed.  It's got a different ID.  Try deleting your WiFi or Ethernet (whichever on is active), then add it back.  You can also just click ok and ignore it, but you'll need to keep doing that.

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newbiewebSr. Software EngineerAuthor Commented:
Thanks. I found I only needed to log in to my iCloud account from iMessage and it worked.
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