@Singing-Phillip You should be able to go to Magix.com, log into your customer account with your e-mail and password and then redownload your old version under "My Products",
Specifically which plug-ins are you missing, are there error messages and which version of Sound Forge? You could try a repair install of the SF version you use.. Uninstalling older versions of SF 'occasionally' removes some of the plug-ins along with it. I always use a third-party uninstaller (Revo) that has the option to pick and choose what related and shared data is removed. Otherwise, multiple versions of SF can co-exist on the same PC without issue. I usually recommend, "If it ain't broke don't fix it".
btw, welcome to the Magix Sound Forge users forum @Singing-Phillip.
So I upgraded and purchased the new magics Sony sound Ford 15… And thought I didn’t need the previous versions… So I deleted them! And one of my favorite plug-ins which is the wave hammer… It’s now not there… The wave hammer surround is there… But it won’t let me use it! It says to make sure it’s properly installed…
As @SP. stated, Wave Hammer is not a part of Sound Forge Audio Studio, I do not think the new (VST) Wave Hammer II is either. btw, WH-II is different .. and it does not float my boat If your reinstall your older SF Pro version, Wave Hammer should become available in SF-AS.. assuming AS still supports the DX plug-in format.
If you had an old version of Sound Forge Pro installed, it would be shared with, Vegas and other Sony and Magix apps, If Sound Forge Pro is uninstalled, so goes WaveHammer with it.