With my Steam SH5, I have had to use the SH5 properties page and change some of the settings there. I assume you do not have the Steam Library folder and game in a Program Files folder, since you say you have had TWoS working previously. Navigate into your SH5 folder, and right-click on the SH5.exe file. Choose "Properties" at the bottom of the context menu list. Then left-click on the "Compatibility" tab, and try changing a few of the settings.
That picture is from my SH4 install, posted in
SH4 won't start after recent Win10 update but most of the same "technique" applies
Your mileage may vary... I have several computers, and each has a different configuration on that properties page. It depends upon your hardware and Windows set-up.
