Hello! 
Firstly, thanks for supporting WeMod by going Pro. It is appreciated. 
This, to me, is ikely to be due to interference from an antivirus program or firewall.
Follow the steps in this post here: I can’t Install WeMod / “There was a error installing the application” - WeMod App / Support. Then try again.
If the issue continues after following those instructions:
- Restart your PC.
- Open your antivirus software.
- Locate the quarantine/virus chest menu.
- If there is a WeMod file in there, whitelist it from here and de-quarantine it.
Keep us updated.