Zoho Assist cannot connect from one uer

Zoho Assist cannot connect from one uer

In Zoho Assist, I can connect to an unattended access machine just fine, but another user tries to connect, gets to the Windows login screen, but cannot type.  CRT-ALT-DEL tool also does not work.  Once she is in, my connection also does not work.  A reboot allows me in again, but as soon as she tries to connect, same problem.  What should I do to diagnose problem?