FLStudio will look for the FLStudio engine. Normally this is the location of FLStudio that was most recently installed. You may want to use another installation of FLStudio, for example an Alpha or Beta for testing ...
Flstudio version 20.6.2
Went to Options and then "manage plugins" and hen went to "Scan options" and clicked "rescan previusly verified plugins" and "rescan plugins with errors but till not seeing any of the
plugins.
Please let me know ...