I am new to Sketchup and have downloaded the Make version but currently it is the trial version of the Pro version.
Not sure if that has anything to do with it but I am also experiencing the same issue where I can not download the Sketchup stl plugin (or any plugins for that matter).
Also, I have tried this on two separate PCs, one with windows 7 and one with Windows 10.
In one post I saw someone mention that if you get the install button then you are signed in but if you see the download button then you are not signed in and you are accessing it from your browser so I have been signing in and using the install button but it displays the window with a fast displayed script that logs me off and returns me to the extension warehouse.
I read in another post that someone added a plugin folder and then they were able to downlad the plugin, but was an older version of Sketchup (ver 8 I think)
Not sure if this would help but can anyone that has this working please post the folder path that their plug ins are located for Sketchup 2016?
Also, I have sent numerous requests for help with this to the Sketchup technical support but have not received a response.
If anyone can point me to a link where I can copy (save target as) to this Sketcup STL export plugin file other than the unusable extension warehouse, I would appreciate it immensely.
Also, if anyone has found a cure for this, please pass it on.