Why does downstairs heating has to be on for upstairs to work?

[Husk24]

It may or may not be identical (how would I know?) but it'll probably sound somewhat similar, i.e. a small motor running for a short period and maybe a clunk at the start and/or end of the travel. If it's a pump rather than a valve it'll running continuously while the zone is active and stop when it's not.

No luck, tried following pipe , listened to noise every room upstairs, no luck im afraid