HMC5883L help needed

Hi all

About 6 month ago after watching a painless 360 vid I decided that I wanted to give inav a try. Everything seams ok with both my omnibus f4s (v3 and v5) it no matter what I tried I could not get the HMC5883L Magnetometer to register…

Just when I was on the verge of going back to clean flight I saw a good deal on eBay for an SP Racing F4 evo so I got the fc and thought I’d give inav 1 last try.

To my surprise the e gps units I had bought all worked including the Magnetometer.

Can anyone help me explain why the f4 evo recognises the mag, but both omnibus boards don’t.

Steps I tried were adding resistors and lowering the i2c clock speed

any help would be appreciated