Won't log into Microsoft account

Morning,

 

the problem I am having is when I try to connect my Microsoft account (which has been linked before) so I can continue to play my purchased packs it doesn't recognise the codes given several times but when it does finally accept the connect code, the title screen flicks off to a loading background I assume but it never actually reloads with the linked account! I have attempted to solve this over several days and as it's my nephews he's getting really upset due to not being able to access his bought levels/worlds. Please help!!

 

also I have no idea if I clicked the right minecraft thing… all I know is it’s switch cartridge and has a market place..

 

Emily