Hi there, @Martajpagan. 

Thanks for taking the time to follow the thread. 

Are you also having some issues signing into QuickBooks Online? If so, have you tried the above-mentioned troubleshooting steps by my colleague, Joesem M? If not, let's use those steps to try signing in using an incognito/private browser.

Here are the steps for all supported browsers: 

• Google Chrome: press Ctrl + Shift + N.
• Mozilla Firefox: press Ctrl + Shift + P.
• Internet Explorer: press Ctrl + Shift + P.
• Safari: press Command + Shift + N.

If you can log in, let's go ahead and clear the cache from your browser. Web browsers collect cache to save time when loading repetitive data and images. Over time these files can become outdated and corrupted, causing issues like the one you're having with signing in. 

Aside from using an incognito or private browser, you can also use a different browser. For example, if you're using Firefox, try Google Chrome. 

Let me know if you're able to get signed in. I'll be around if you have further questions or concerns. Take care!