You can MOVE ALL Plugins out of the Plugins folder and try to start the app without ANY Plugin and see if this works. If yes then you can move back the Plugins one after another and try to start vStudio so that we can see if the problem is related to a single Plugin only!
Using menu HELP → PLUGINS open window about plugins. In the line of “Valentina 3.x File Plugin” you can see “Valentina Engine version:3.6”. Sometimes you need increase the width of window to see version.
Try this please. Open Preference dialog of Valentina Studio app. Click button “Show on disk”. Quite application. Trash or just remove that folder with prefs files. Start app again and enter your serial.