You did not clearly specify which pass and where you want to buy-but I suspect via this site the mobile version on app? In that case its likely banned through some system parameter (this is just my guess, Ive accidentally bought a pass yesterday-as paper and I am long since >60).

IF this is indeed the case, then I suggest to try another outlet or use the old-style paper pass, this should be able to buy on showing ID.
note that NOW there is 2x 10% discount- by age-as always-and an extra 10% off that due to promotion for 50 years InterRail.

Now I see de er dansk. DSB-on only some major stations, sell still the old-style paper pass so you could also try there and show your ID/passes. The extra discount is till 31/3, but for paper pass you have to state what is the starting day-cannot be changed afters.

Hi Thora, apologies for the late reply. I hope you got your answer from our customer support team in the meantime, but if not I have the answer for you. We are currently working on a fix as you should be able to order a senior Pass without a problem. In the meantime we offer the following workaround: You can purchase the Adult Pass for your husband and contact Customer Support afterwards. They will refund the price difference.