Is it forbidden to go to coffee shops, and is it true that the prayer of one who goes there is not accepted for forty days? What are the proofs for this from the Prophetic Sunnah?

There is no Hadith (definition) that prohibits going to a cafe, or that states that one's prayers will not be accepted for forty days if they go to one. However, if this cafe is a place where forbidden acts are committed, such as drinking alcohol and looking at indecent, forbidden images, then it is not permissible for a Muslim to be present in such a gathering where Allah the Almighty is disobeyed, due to the saying of the Prophet, peace and blessings be upon him: "Whoever believes in Allah and the Last Day, let him not sit at a table where alcoholic drinks are circulated."