IP Phone not working on HP 1920 switch

Hello

We have HP 1920 (JG924A) switch at remote location. Having only 1 VLAN (Default VLAN - 1). All ports are access ports. Switch HP 1920 is connected with another uplink switch HP E-3800 that too has only 1 VLAN (Default VLAN-1) all ports are untagged in VLAN 1. That switch HP e-3800 is uplink with Cisco router.

There are PC / workstations , printers, IP Phones. All of them working fine on HP-E3800.

But IP Phones are not working on HP-1920. Able to ping the IP phone but service is not working. When shifting IP Phone to HP E-3800 it works fine.

Help needed.