I am not managing to pay with credit card as formerly.
The site changed settings and only see an option that “coupon code” and no longer has that of credit card option.
I am sorry to hear that you’re having issues with upgrading your account. I’ve just checked this and everything seems to be fine. You should be able to upgrade it with credit card in the Account Page (https://www.lingq.com/accounts/account/). Let us know if you still have trouble with this.