Outlook mail with error "Mail could not be received at this time"

I use Outlook for my mail on my MacBook Pro. It has been working fine till I have been getting the "Mail could not be received at this time" error. It prompts you to enter your password for the gmail server but does not accept any that I use. I had Outlook preloaded when I bought my laptop just over a year ago. This is my first Apple laptop and I love its functionality but struggle when such issues arise. Appreciate any help.