I am running PtK 2.6 as a paid subscriber, using the Safari (14.0.2) extension under Mojave (10.14.6). This morning, I installed the new Capitol One Shopping (formerly Wikibuy 1.0.6) extension. and it prevents 2.6 from working. The PtK toolbar icon tries to open the PtK page, but then hangs.
P for K 1.6 still works.
PtK 2.6 will work if I uncheck the COS extension - that is, I don’t have to uninstall COS to get 2.6 to function properly.