I need help configuring VLANs through some new Mikrotik switches. They are CRS-326-24G-2S+ running 6.43.2.

I have read through both these examples and tried various configurations based off of them: https://wiki.mikrotik.com/wiki/Manual:I ... Based_VLAN and https://wiki.mikrotik.com/wiki/Manual:C ... s#Features

Here's my situation: I'm trying to help out a school. They have a SonicWall router with school network of 10.10.1.x, and a guest network of 192.168.252.x on VLAN 252. The have Ubiquiti UniFi APs running two SSIDs: School and Guest (with VLAN 252).

The SonicWall feeds a Mikrotik CRS-326-24G-2S+. From there they have a couple old D-link PoE switches with APs off them. Those D-links have VLAN 252 tagged on the Uplink port & on the ports for APs. Everything there is working as it should, but there is no VLAN configuration in the CRS switch (Switch A in the diagram).

In another building they have another Mikrotik CRS-326-24G-2S+ (Switch B in the diagram). This is connected to Switch A via fiber. The school network works just fine, but the guest network will not work. No IP addresses are handed out DHCP and even with a static IP there's no network connectivity. The VLAN is not being pushed through.

Since the D-links work, I tried only configuring Switch B. But that didn't work.
Switch B
add bridge=bridge1 tagged="Eth2-Uplink from Switch A, Eth20-UAP" vlan-ids=252

So I added tags in Switch A. But still it didn't work.
Switch A
add bridge=bridge1 tagged="Eth2-Uplink from SonicWall, Eth 5-Link to Switch B", vlan-ids-252

If I enable VLAN filtering on Switch B, there's no change. But if I enable VLAN filtering on Switch A I lose the school network off of Switch B.

What am I missing? And why do the APs off the D-link switches work without any configuration in Switch A?