As Microsoft changed a dependency for the SEB 3.2 installation, the previous installer fails. The issue has been fixed in the new SEB build 3.2.0.338, which is identical to the original release, but installing the WebView2 dependency works again: https://safeexambrowser.org/download
If you really need to install SEB 3.2.0.324, you can always install all the below listed dependencies manually and then run the MSI setup for your platform:
.NET Framework 4.7.2 Runtime: https://dotnet.microsoft.com/download/dotnet-framework/net472
Microsoft Edge WebView2 Runtime: https://go.microsoft.com/fwlink/p/?LinkId=2124703
Visual C++ 2015-2019 Redistributable: https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads
SEB 3.2.0.324 (x64): https://sebdev-let.ethz.ch/api/buildjobs/tgvq4q38nexl26m0/artifacts/SEB_3.2.0.324_x64_Setup.msi
SEB 3.2.0.324 (x86): https://sebdev-let.ethz.ch/api/buildjobs/nqsuhaewxy4rengp/artifacts/SEB_3.2.0.324_x86_Setup.msi