No Wifi when adding second SIM to Realme phone

[#1]

As above. Wifi (as in home router's wifi) works fine with one SIM. Adding a second it doesn't.

Grateful for any ideas.

[#2]

Try 

Settings >Wireless & Networks> Dual SIM Settings .check on there for  all the settings for both SIM1 and SIM2

[#3]

Thanks, had already checked that.

[#4]

Did you try swapping SIMs positions in the tray (or whatever SIMs are held in)?

Is the WiFi completely off in that scanning finds nothing or some other problem?