Contact the support for the bonus. Betpanda bonus sometimes goes blank or unavailable if you didn’t claim immediately.
I encounter a lot of bonus like that including free spin. I manage to recover some by contacting the support. But I suggest to hard reset your browser and login back again.
I believe this is the last suggestion made by support that helps me to see blank bonus on my bonus inbox.
It is reasonable that there is a claiming period after that your bonus will become invalid. I don't have experience with Betpanda and their marketing programs, fro example bonus program, but if they have such terms, I agree with them.
If they have such term and mention it clearly in their bonus or marketing programs' terms, as well as have at least one time of warning message for program participants or even after those participants are eligible for such bonuses, I see they do all necessary steps to inform their users and program participants about that.
On user and participant side, if they ignore all those information, and miss claiming period, it's their responsibility and surely after time is over, Betpanda team can not help anything.