When FortiClient stuck on connecting try
Download and install the VC Redistributables.
MS Visual C++ Redistributable for Visual Studio 2015-19, or 2022
x64 (64-bit): vc_redist.x64.exe
https://aka.ms/vs/17/release/vc_redist.x64.exe
That should help. If it doesn't, download the x86 version as well.
x86 (32-bit): vc_redist.x86.exe
https://aka.ms/vs/17/release/vc_redist.x86.exe