Have the same problem!

I have the same problem

There seems to be a certificate issue on the website that shows when logging in. Probably the certificate expired.

The same issue.
It's unbelievable. We are paying money is it so hard to renew a certificate on time?

Yes this definitely certificate expiry. I wish the doit team would fix these issues! As I posted in another thread: doit.im's certificate has expired and iOS won't allow an HTTPS connection with an expired certificate. The app won't sync with the web version until this is sorted. You will find that the web version is the most accurate view of your tasks if you proceed through any browser security warnings (e.g. in Chrome you must click Advance and Proceed to i.doit.im (unsafe)). Unfortunately the file upload does not work in this forum but here is a link to a screenshot of the certificate expiry hosted on ImgBB (https://imgbb.com) - https://ibb.co/ZWLnHF5.

Text version:
*.doit.im
Issued by: COMODO RSA Domain Validation Secure Server CA
Expired: Thursday, 10 October 2019 at 10:59:59 Australian Eastern Daylight Time

It's unacceptable to leave a service down for more than 4 days, considering that with services like Let's Encrypt they could generate a certificate for free.
I don't know why Doit staff act in such ways, hope nothing bad happened because if they're thinking about closing their product they should publish an announcement about that. We have been loyal customers for years, for one of the best GTD app available out there, we deserve a fair treatment

Woohoo, looks to be fixed now!

Certificate contents:
*.doit.im
Issued by: Sectigo RSA Domain Validation Secure Server CA
Expires: Thursday, 14 October 2021 at 10:59:59 Australian Eastern Daylight Time