Due to a Flamingo bug I had two versions of Flamingo installed on the same computer:
Flamingo nXt 5.0 --–and— Flamingo nXt
These two versions were in conflict, so I tried to erase the older one (Flamingo nXt 5.0). It did not work, so I tried to erase both of them. It did not work, so I erased Flamingo registry: \HKEY_CURRENT_USER\Software\McNeel\Rhinoceros\5.0x64\Plug-Ins\fd53f8c4-546d-47d1-8820-e66c97645a97
I still cannot get rid of Flamingo. As you can see in the following screenshot, the Options command shows two Flamingo plugins. The Flamingo nXt 5.0 menu does not work. RT Flamingo tabbed panel does not work either, but its name is listed on the panel menu. ToolbarReset command did not remove the Flamingo nXt 5.0 menu.