Hi,

IGMP should be enabled globally by default. Page 613 multicast VLAN may help you. https://downloads.dell.com/manuals/all-products/esuprt_ser_stor_net/esuprt_networking/esuprt_net_fxd_prt_swtchs/networking-n1500-series_user%27s-guide11_en-us.pdf

Is there a way to ensure the multicast traffic will propagate to every switch with that vlan even if the traffic needs to traverses several up-links?

Basically, we've had difficulties with having igmp groups show up across multiple network switches.

There isn’t a command to force it that I see, you would probably need to use wireshark and figure out where the packets are not being sent.