Reactivating Antivirus and SecureLine on Android

After upgrading to a custom Nougat rom, I cannot get Avast products to work: SecureLine wants a voucher, which I cannot locate, and with the Antivirus the license text won’t open automatically and there’s no “subscription” option on the settings. tab.
There’s not much time left on my subscription, but I will not renew unless the current products work.
Support conveniently ignores me.
Can anyone help, please?

Custom roms are not supported.

https://www.avast.com/faq.php?article=AVKB64