Thanks, Jason.
This is how I solved it:
https://myaccount.google.com/u/1/security
Scroll down to Connected Apps & Sites, then look for the following:
Allow less secure apps: ON
Some non-Google apps and devices use less secure sign-in technology, which could leave your account vulnerable. You can turn off access for these apps (which we recommend) or choose to use them despite the risks.
Make sure Allow less secure apps is ON.
That helped me solve my problem :)