guest unable to book

[Nemanja0]

Hi, I am new to this and so far I have been having two successful hostings so to say. But from today two of the potential guests who would like to do the booking cannot do it - they receive the message that it is not possible to do that?

What is happening and who do I contact. 

[Karyo0]

It could be for a number of reasons - Are they asking for dates that you are not available? Are they asking for 1 night and you have a minimum 2 nights? are there more guests than you allow? Are they new airbnb users that have not verified their account?