Q: How to resolve problems with file sharing?

I have a newer iMac and a 2009 Macbook Pro.  The iMac can connect to the MacBook, use screen sharing, all with no issue.  However, the MacBook can not connect to the iMac unless it connects using the "Guest" option.  I have "Back to my Mac" enabled on both computers.  Trying the "Registered User" and "Using an Apple ID" option to no avail.  Both of these computers are on the same home network, sitting side by side.  It's unfortunately, but home networking has been the least "easy to use" feature since migrating from a PC years ago.

Any suggestions?

Thanks