Hi Simon%20Sch,
In this scenario where you are clicking on allow however nothing happens after that, please let us know if this is the first time you are installing the Adobe Creative Cloud desktop app on this machine, or was it installed on this machine earlier as well?
If this is the first time installation then i would recommend you to follow the below steps and try the installation again as the below could be blocking the app from getting installed:
1- Temporarily turn off security/Antivirus program installed on your machine completely.
2- Turn off any browser security add-on's installed on your machine.
3- Turn off system Firewall temporarily.
4- Reset the hosts file. See, Advanced solutions to connection errors with Adobe Creative Cloud and Creative Suite applications .
But, if this is the second or third installation of Adobe Creative Cloud desktop app on this machine, then please refer to the troubleshooting steps mentioned in the following help document: "Failed to install" error received when installing Adobe Creative Cloud desktop app .
Kinldy let us know if this helps.