Challenge limit reached - What can I do to prevent this?

Question

Why do I get sometimes the following message:
"Challenge limit reached
complete your ongoing challenges and try again."
At the moment there are only 5 challenges running and in all of them I am waiting for the opponent.
There were days when there were dozens of waiting opponents and I did not receive that message.

Answer 1

It is possible that you have reached the challenge limit with a specific user. All members are limited to a number of 15 challenges per day with another member.

Answer 2

It is per one day

Answer 3

Hi Hatsy Rei,
thank You for Your answer! That makes sense!

Answer 4

I discovered that I had 15 challenges with one person yesterday. But some two days ago a had further challenges with this person ago, so I assume that the limit is unlocked after one or two days.