Two Macs on LAN connection: 10.5 machine sees 10.15, 10.15 does not see 10.5, transfer cannot be initialized either way

[barracuda156]

Machines connect normally via Finder or ssh. When LAN-Share is running on both, a Mac with 10.5 sees a Mac with 10.15, but not the other way. Sending file does not work even from the machine that sees another. Any idea what may be going wrong?