There's another link between those two switches that's forwarding and so Spanning Tree has blocked this other link to avoid a loop. LLDP (or CDP) should give you a good starting point to working out which port goes where.
Assuming some "security" team hasn't disabled it...
there's a special circle of hell reserved for people who block ping and ICMP unreachable, along with those who shut off lldp/cdp on switches.
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