I can't seem to install the T3 2.5.5 update to my WAMP installation. I did it once before in a previous update. At that time, on a fellow member's suggestion, I think I zipped the plg_system_t3 folder (in the T3 full installation downloaded ZIP file) and then installed it using Extensions > Manage > Install > Upload Package File. Whatever I did at that time, it worked fine.
This time I tried uploading the zipped plg_system_t3 folder, as well as uploading the entire T3 full package Zip file. In both cases, it looks like it's doing something for a few seconds and then it's back at the same screen, having done nothing; my T3 has still not been updated. I've updated Joomla to 3.5.1, and need to update T3 as well.
What am I doing wrong? Thanks in advance for the help.