What address do you use to log into the webmail and what username are you trying with?
To login to the webmail, use the following address: https://webmail.loopia.se.
The username for the webmail (and other email clients) is your email address (for example firstname.lastname@example.org).
If both the address and username are accurate and you know that you are using the correct password to the email address, it is probably a setting in your browser, an antivirus software, ad-aware or HTTP proxy that is blocking the cookies the webmail is trying to set to verify that you are logged in.
If you do not have such blocking of cookies, it may be that the password is wrong.
You can set a new password for the email account in your customer zone by choosing the domain under the title called “E-mail addresses”. An option to edit the email will show on the panel which appears and you will then be able to enter a new password.