For me, it was the internet security software (zscaler) on the work laptop that caused the error. The site itself worked, only the download ran into above error. Took me a while to figure it out ;)

For me it worked like a charm- except for the fingerprint Calibration software via https://pixelrepair.withgoogle.com/udfps

My Pixel is connected in Fastboot mode, and when I try to start the procedure I get stuck at step 1 "downloading the software"

"Couldn't download the software"

Anyone else facing this issue (or haveing a fix for that?