I use the TAP plugin as described.
Although the results seem to be reported correctly when I view the TAP file form the jenkins menu option it seems the format is not OK. Newlines are missing.
When I run the Python script that produces the TAP file from a terminal I get correct file.

I checked the TAP file in the build directory and this is also OK so it seems a problem of the HTML presentation.

In the webpage it is like this:

1..2 ok 1 login successful not ok 2 No heartbeat message