First game of the season and nobody's cards work. Must be 500 people queuing outside.

Yes, I gave up after getting to the front of 2 different queues, at that point they said go to the ticket office and at that point I came home, my blood pressure was already near boiling - the ticket office (marvellous people though they are) would just have tipped me over the edge.
Have emailed customerservice@quins.co.uk and will expect some anodyne response from James Swanson in the fullness of time.

But how could this happen? Did they not test their scanners/software with both new and old cards? They must have surely?
And why was there no-one with sufficient authority there who could have checked my card, checked my photo id, noted the membership number for later and then let me in? My driving license has my home address on it - they just had to note my member id, house no and postcode and they could feed it in the computers later. Yes, in theory I could be using last years card and not paid for a season ticket this year and be trying to sneak in but honestly, what is the likelihood?

This is a spectacular own goal from the club. Spectacular!

I have mine but never used them. And a quick check from the club could have told them that and that perhaps I needed to be reminded which card to bring?

And why did no-one tell the stewards or the scanner operatives this vital piece of information? No-one said to me "Ah, you are using the wrong card. You need the VISA one"

Found it on the email they sent "Your Team to Face Worcester Warriors" (obviously requiring a completely different card for entry is not important enough to warrant it's own email! )

After "YOUR TEAM TO FACE WORCESTER WARRIORS"
After "PLAN YOUR DAY - HARLEQUINS V WORCESTER WARRIORS"
After "BARS, CONCESSIONS AND FACILITIES"
After "THE CLUB SHOPS"
You finally get to "MEMBERSHIP CARDS".
"Season Ticket Members will be using their Membership card to enter stadium for the first time. Please remember to bring this with you to scan at the gate. Please don’t bring your old non-VISA Membership cards as these are no longer activated for entry."

You might think this should be in bold red type, but apparently it's just an unimportant reminded like where the shops are.

First game of the season and nobody's cards work. Must be 500 people queuing outside.

Mine worked

But how could this happen? Did they not test their scanners/software with both new and old cards? They must have surely?

This is a spectacular own goal from the club. Spectacular!

Why test with the old cards? They issued new ones!
The only own goal is with you. Certainly seems lots of people got in without any problem.

Got in first time, a few in front did not, used the Visa membership card fine. And I've never activated it for payment, it's simply to get in the ground as a standard membership card, simples. Hope those who had issues will get them sorted by the next game in a couple of weeks.

I used Visa type card and didn’t get in, at first then they let me in

Eddie Jones, Cockers and all the other English coaches got in.