I just started using k-9 mail yesterday but then when I check my inbox today it was not updated. There’s no new emails though checking my email in web I supposed to have some. tried to refresh but still the same. also tried to check setting configure.
Without infos nobody can help you.
Device
Android version/rom
K-9 version
Email provider
POP or IMAP
Pull or push configured
Server settings/type of password