Yes, 7510N do support UPnP and multicast, they don't need to enable in management web,also I think you can try access 7510N in house 2 and your dlna server from house 1 host at the same time to see if this problem is related to your 7510 or wireless connection, while in fact, I don't know so much how your dlna server communicate via this wireless link
besides, as I know, this model 7510 is eol from TP-LINK official for long ago, now the pharos series CPE510 is the recommended.
may this message useful to you

Whole LAN works OK. All devices are accessible from house 1 and house 2 and viceversa. From house 1 I can connect to 7510N in house 2. Over ssh I can connect without any problem from house 1 to computer on which DLNA server runs, but DLNA is not accessible only from house 1 part. Can be issue with security type? Now I have configured WPA2-PSK (AES) security on both devices. If I remember corretly, this problems starts when I changed security type in both AP and Client to WPA2-PSK. I tried to configure devices as Bridge with AP but issue with disconnection is not fixed as is mentioned in http://www.tp-link.com/us/faq-463.html. But in Bridge with AP mode is only WEP security type supported and speed is decreased to 54Mbit/s. When command "nmap -T4 -F 192.168.1.0/24" is executed from both sides I got same result. With my phone which have 5GHz module I tried connect directly to 7510N in house 1 and checked if VLC lists dlna server but without success so only problem can be in connection between AP and client.

Thanks in advance

Ok. I found the issue. Problem is definitely in connection between AP1 and AP2. Connection AP <-> Client not working correctly (bugged as whole TL-WA7510N device). When I changed each device to Bridge with AP and set security type as WEP everything woks correctly. But this is not suitable for me because:
- WEP is insecure
- speed is decreased to 54Mbit/s
- Bridge with AP loosing connection after while (bug is not fixed as is mentioned in http://www.tp-link.com/us/faq-463.html)

This device was unable to broadcast the maximum noise? Could not interrupts?
TL-WA7510N