Any idea why I can log in on one computer, but not the other, with exactly the same user and password, perfect case and copy?

What is the browser in the computer where the login works? Is the other computer using Chrome or Explorer? We cannot reproduce the problem in our side, so please provide us as much details as you can.

The effect occurred with Firefox on both computers.  The computer on which it failed at that time, did allow access today.  My guess is that perhaps your system is sensitive to access to my account by more than one computer at a time, and my attempts to access by two computers prompted that failure.  (One computer keeps freezing, so I tried to access my account from another computer, while I was unable to use or close the account on the first computer.)  If my guess is correct, I would be interested to know.  Otherwise I will not be concerned, unless the problem returns in an event of only one computer accessing the account.

It is possible to login to your JotForm account on different computer simultaneously or all at the same time. As long as you know the login credentials, you should be able to login to the account on different multiple devices even if all at the same time.

It is possible also that you have encountered the login issue on the other computer because of problem on that computer (browser) only and not related to your JotForm login.

You can also review any activity logs on your account in the history logs section of your account.

User guide: https://www.jotform.com/help/370-How-to-View-Your-Account-Activity-Logs

Let us know if there's anything else we can help you with.

The problem did not occur on the computer with the browser issues.  Since have been able to log on since then, anyway, I will leave it alone - unless and until it reoccurs.

Thank you for your attention.

Thank you for the clarification. Please don't hesitate to contact us again if the issue persist.