Unfortunately, the policies for what's an acceptable password varies and is determined by the folks responsible for computer security. I can't remember what the password rules are on JOF but, generally, all passwords seem to have some limitation of minimum/maximum length, what special characters, if any, are valid and whether there are any special rules in place like the password must contain a certain number of upper/lower case letters, numbers and special characters. I've run into situations where the first character of the password must be alphabetic, so if the new password you're creating starts with a "1" or a "#", the password would be rejected if that's their rule.
Being that you have a current working password, I would suggest making your new password the same length as the current one and use the same number of letters, numbers and special characters. I think this will increase your chances of success.
I hope what I've written here will help.
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