vlan stopped passing on single switch

[aistech]

Netonix ws12-250 v1.5

I have a vlan 607 that follows this path which has been working fine for months.

<CiscoRouter>-------T<Netonix1>T-------T<Netonix2>T-------T<Netonix3>T-------T<Netonix4>T-------T<EndDevice>

This morning, I lost communication between the Cisco and the End Device over vlan 607. Tracing the problem from the endpoint back, I found that at Netonix3, the netonix can no longer ping the Cisco router over that Vlan, Netonix 1&2 can ping the Cisco just fine. However, I have a second vlan, 606, following the same path and all is well end to end.

Any insight would be greatly appreciated.

Thank you