TrendNet TPE-1020WS switch SNMP timeout if behind other switch

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Hi, I have two HP ProCurve 1810G-24-v2 switches, and two TrendNet TPE-1020WS POE+ switches in my network.

If I connect my PC directly to a TPE-1020WS, I can get SNMP info from the switch.
If I connect from a PC behind a 1810G switch, SNMP times out.

This makes no sense to me as other devices respond just find to SNMP even if behind two 1810G switches.

Any ideas why the TPE-1020WS switches would not respond to SNMP when behind another switch?

P.