I hope this situation will be resolved before it affects anyone (including me--my current hotel reservation runs out on the morning of September 20). If you're connecting from Turkey, Booking.com has a pop-up announcement saying it's only possible for customers in Turkey to book international properties at the moment. Actually, it's not letting me enter domestic destinations at all and international destinations aren't working well, either; there's less information than usual being shown on the list of available hotels. Basically, the website is pretty much broken if you're connecting from Turkey.
It's inconvenient for me, because I plan about 20 more days in Turkey, and I don't want to extend at my current hotel. If the issue isn't resolved soon, I'll have to do my initial research on a different website. The horror! I really like the booking.com reviews.
I don't know whether a VPN would allow me to avoid this problem, but that's too much hassle for me.