Anonymous Calendar Sharing URL in Exchange is not working between Exchange 2016/2019 coexistence

Hi guys,

(Scenery)

I have 4 Exchange Servers 2016 CU22 Frontend; Only CAS Function | CAS Role

I have 6 Exchange Servers 2019 CU9 Backend; Only MBX Function | MBX Role

(Flow)

Internet ==> HLB (Hardware Load Balancer) ==> CAS ==> MBX

PS: Exchange Server 2016 CU22 is kept as CAS Role to maintain compatibility with older email clients.

All users when accessing shared calendar settings get this error <HTTP ERROR 500> below using Exchange Server 2016 CU22 with proxy function.

But. if i access directly through an Exchange Server 2019 CU9, the feature works perfectly.

Follow the configuration:

Any ideas guys?

T