This happens sometimes on startup when the blockchain either hasn’t been sync’d yet, or is quite a bit behind, which cause zcashd to take longer starting up.
You can get around it by starting zcashd.exe manually in a terminal window, preferably PowerShell, with the command:
c:\Program Files\zcash4win\app\zcashd.exe -daemon=0 -showmetrics=1
It’ll display the block height that its sync’d to, and you can compare that against a block explorer like https://zcha.in, and once it has caught up, launch the GUI.