I'd like to thank everyone for their kind responses. One person who responded off list and bothered to look at the returned certificates pointed out, and correctly it seems, that my original setup was missing an intermediate certificate. The site was returning 'valid ssl' and all browsers got the green lock and offsite ssl tests came back ok, but apparently the missing intermediate means it would have had to have been fetched and that was the part that was failing at the customer site. Once I put the intermediate certificate in there, the customer site was able to access https without fail. I have not had an opportunity yet to examine in detail the config of the meraki router there but it's either a routing problem or a DPI problem. If I get an answer I'll post again with my results. Thanks all. Mike-