I just went into 4.2.1 Admin control panel. I removed the old plugin.
I had previously attempted to install the tapatalk_ipb-4.2_v1.4.0.tar and tapatalk_ipb-4.2_v1.4.1.tar and received errors with both.
That said, when I scrolled down on the "Applications" page there was a section at the bottom I had not noticed before called "Applications not currently installed". Tapatalk appeared in the list so I clicked the "+" (install) button. It then installed and appears to be working.
I do not see anywhere to input my Tapatalk API key. Is this no longer required?