I was receiving the message when trying to download the wallet not install it.
I tried to download the new version of the wallet today for Windows and did not encounter the same problem as yours.
1. When I clicked the button "Windows" on unify.today I was redirected to google drive ↓
2. No preview, but still I clicked "Download" and Google Drive states that they can't scan the files for viruses ↓
3. I clicked "Download anyway" and decided to scan the file after (zipped and unzipped, there were no threats detected).
4. I successfully downloaded and Run the wallet.
5. It's currently syncing, if ever problems occur with that, I took note of the add nodes (sharing here for reference)
addnode 67.205.144.6 add
addnode 94.19.225.139 add
addnode 188.233.90.147 add
addnode 165.22.53.180 add
addnode 94.130.129.84 add
addnode 71.254.203.190 add
addnode 213.118.251.144 add
addnode 89.130.100.78 add
addnode 84.106.73.205 add
addnode 67.244.70.190 add
addnode 88.114.0.89 add
addnode 93.41.115.186 add
PS. I was away since January and glad to know that there have been improvements. The team didn't stop working for Unify.