External Sky’q box not working

[John-Thomson-]

I have a skyq system as follows 

main box in lounge next to router and main Tv

2nd mini box in upstairs bedroom with a booster box in adjacent room

3rd mini box in man cave in garden connected vis Ethernet to mini box 2 

All systems worked fine for past 2 years but box 3 in garden stopped receiving internet

no damage to cables 

help if you can

[NickNewark]

@John-Thomson- Have you tried a network reset on it, which you can do through the Sky Q menu