you are wrong. all my active plugins are targeted to 4.8
Has it been like that for a while? I'm sure at one point I incrementally increased the net version until I got an entry point error to determine how high I could go. I guess that was probably a couple of years ago now.
Anyway, that didn't fix it but I have got it working on my other machine (PC2) although I'm not sure exactly what the problem was. I'll go through the steps I took.
PC2 had a portable install with an older version of Musicbee and the VUMeter plugin when it still had separate sharpGL DLL's.
I deleted the SharpGL dll's from Musicbee\plugins and copied over the mb_VUMeter.dll and Musicbee.exe from my main machine (PC1).
At this point it wasn't working.
I tried setting the output to Net 4.8, this worked fine on PC1 but still produced an error on PC2.
I deleted the entire Musicbee folder on PC2 and copied over the entire Musicbee folder from PC1.
It now works on both PC's.
The only thing I can think of is maybe there was another copy of SharpGL.wpf.dll in the Musicbee\appdata\plugins folder.
So maybe have a search for SharpGL.wpf.dll and delete any instances you find. If not create another fresh portable install and see if that works.
If you still don't get anywhere I'll send you a copy that will display an error if it's the same problem my PC2 had instead of just giving you a blank screen with no info. Just in case you are having a different problem than my PC2 had.