[ms660]

Works ok here on my PC....eg: Simpson:

https://www.schematicsunlimited.com/s

https://www.schematicsunlimited.com/s/simpson

https://www.schematicsunlimited.com/...eter-schematic

Then I filled in the verification code and hit download and the schematic downloaded ok no problem.

EDIT: Post crossed with Robs edit.

Lawrence.