Button "Weiter" "Next is missing in Self Signing

We are using the Self Signing Function in Adobe Sign and also combined with Acrobat Reader.

With Adobe Sign (in the Adobe Sign Cloud) everything is running as well with "self signing"

For the function in Acrobat Reader we identified and issue for some users  and we still not understand what could be the reasong. The issue is on different machines with different lnagueages.

The Button "Next" (EN) or "Weiter" (DE) is missing for some users. Without this button the process can not be completed. See 2 examples (SelfSigning_German - Button is available, SelfSigning_CZ - Button is Missing)

We have this situation in different languages (see example in CZ) - the button is missing. All of our users are using the same Acrobat Reader Version. This is distributed as a company solution. Version DC 2021.007.20099

The affected user have the rights in Adode Sign and it is working as well in the cloud. So it seems that the  permissions is not the reason.

What can cause that a button is missing and how can we resolve it?

The main problem is - we can not provide this function to our user, because we do now know how many users are affected, could be thousands - and we have no solution for this.

Please support.

Thanky in advance.