Don't know what went wrong. After trying a few times, I got it. However, I still cannot share files.
Under Locations>Network on my MacBook Pro, Mac mini is listed. Doubling clicking showed "Macintosh HD".
There are two options:
When I double clicked on it again, "Loading..." for a long long time and then the system showed:
"The operation can't be completed because the original item for "Macintosh HD" can't be found."
When I clicked "Connect As", it took some time for the "Enter your name and password for the server "Mac mini". "Connect As" Registered User. Entered my password and clicked Connect. Then, double clicked "Macintosh HD:.
Again, "Loading..." showed up for a long long time and then the system gave me that "The operation can't be completed because the original item for "Macintosh HD" can't be found.". Using "Connect As" Guest ended up the same problem.
Both computers have file share On. Under Network of MacBook Pro, it shows Thunderbolt Bridge Self-assigned IP with a yellow dot.
Both are running 13.2.1