SMB Password Rejected When Connecting from One Mac to Another Via Ethernet File Sharing

I figured out the answer to this issue, which is posted here in the Apple Community: https://discussions.apple.com/thread/1265858

and here in MacRumors: https://forums.macrumors.com/threads/file-sharing-password-rejected-from-one-mac-to-another-but-not-the-other-way-around.2079682/

I was trying to connect to my old iMac via an ethernet cable in order to transfer some of my files to my new Mac Mini. I was seeing the old iMac as an available computer on the network, but when I entered the admin username and password for the old iMac, it was rejecting it as a wrong password.

First I tried resetting the old iMac password but that didn't solve the problem. The solution was the one posted in the MacRumors forum: On the machine I wanted to connect to (the old iMac), I went to System Preferences > Sharing > checked the checkbox next to "File Sharing" > Added the shared folders I wanted to share under "Shared Folders" (my admin password was shown as having read and write permissions > Clicked on the "Options" button > Share using SMB and Share using AFP were already clicked -- Under "Windows File Sharing," I clicked the checkbox next to my admin account > entered my admin account password. IT FINALLY CONNECTED.