Meraki Fiber issue

I have an issue I would appreciate some insight on trouble shooting some fiber connecting meraki switches.

Backstory: A warehouse with 4 switches connecting A-B-C-D

They all have 2 connections from their uplink switch. Switch B-C technically will have 4 as they have downlinks to the other switches.

Multi mode OM3 fiber 12 strands terminating to a fiber patch panel.

All the same SFPs from meraki directly ( forget the exact model rn but can update later. It’s the LR multi mode rated for the type of fiber we were told is in use)

Switch A-B : No issues Switch C-D: No issues

The problem...

Switch B-C

I get no link from either port no matter what I try.

I have swapped and tested with known good SFPs and patch cable ( in fact I verified they weren’t bad as well but putting them in a working port and it came up zero issues)

I tried this with both switch’s btw

I have tried all strands of fiber no luck.

We had the cable vendor that installed it “test” it but they were kinda incompetent about the whole process and didn’t get test results printed.

I’ve tried explaining this to the PM on this project about how we can’t just take their word for it because their response was “we got light to go down it “ which I’m not super familiar with fiber testing but I know at least the intensity of the light and signal strength is kinda important to actually getting usable fiber.

Unfortunately we don’t have the tools ourselves to validate this but I wanted to know if anyone had any insight on this and could offer something that maybe I missed or I’m on the right path and there is something wrong with the Fiber itself running from those switches. Luckily this warehouse has a barebones crew in there running off of wireless so an RMA process if needed wouldn’t be too painful but the longer this sits it could be an issue.

Thanks !