If you have trouble logging in, you should perform the following steps:
1. Check that the Date and Time (including time zones) of the device in use are correct.
2. Clear Cookies and Cache in your browser settings. Then carry out the operation indicated in the following GIF at the end of clearing them:
Once these operations have been carried out, update the page using CTRL + SHIFT + R.
If the problem persists, close and restart your browser after removing the cookies and try to log in again.