I tried on three routers, one with 7.24.5 and and 2 with 7.26beta3. One would need a proxy, but other have a public address. /ip/cloud all setup, no error on "File Share", nor in logs. But it never connects using the either the ?dl URL or the direct one.
Now I have not tried BackToHomeFile is a few months. And was going to use for something, and then it does not seem to work. I'd say maybe my network, but the three routers I tried are all on different networks to narrow this down.
I can dig more into what's going on... But if BTH Files was disabled as part of the recent vulnerabilities, IDK, or just a temporary outage... or perhaps bad luck and misconfiguration on my part. But the DDNS resolution always report a fixed IP that does not respond to ping, even when a direct connection seems possible.
If anyone uses "File Share" aka BackToHomeFiles..., if they can report if it's working for them, that be helpful. I may try more devices, or look at sniffer/etc... but if I play end-user here, BTHF looks busted.