I have a macbook pro and mac OS Big Sur 11.2.3, I have tried all the things you said, but there's no "open anyways" option either. And the file is 90.7mb. I paid $2 for it and tried downloading both free + paid options and always get the same message. I have a wired logitech :
Viewing post in iVIBRATE Ultimate Edition comments
It looks like you have bought iVIBRATE Pro Edition, whereas this is the project page for iVIBRATE Ultimate Edition. iVIBRATE Pro Edition is a deprecated version that is no longer supported. iVIBRATE Pro Edition is provided as is, so if it does not work for your system unfortunately there isn't anything I can do about it as it is an old version of iVIBRATE running on an old input system.
The only thing I can suggest if you cannot get it working on your system is to contact Itch support here and request a refund. If you are still interested in iVIBRATE, you should try out the demo versions first to check for compatibility before purchasing. :)