This article gives you a clue, what you can do if your login to NAS failed.
If you have a new NAS 326/540/542 or you already use it for a while, but for some reason, you can't get to the configuration page anymore you may have installed an anti-virus software like Bitdefender. In this article, we show you that antivirus software like Bitdefender can cause problems with the connection and how to fix this (by problem with Bitdefender).
Per default, the NAS is configured as a DHCP client and therefore will get an IP address from your router/network internal DHCP server. Anyway, it should be accessible by http://NAS542 (for a NAS542) and the default login is admin/1234. The login page looks like this:
A successful login looks like this:
Right after installing Bitdefender you can't log in to your NAS anymore. The site is shown correctly, you can enter username and password but it won't log you in.
If you then have a look in the control panel of Bitdefender, you will find a new notification:
It tells you that Bitdefender blocked an unencrypted connection to the IP of the NAS. Here you also can add this connection to the exceptions.
If you have dismissed this message already or don't get this message at all, you also can also create the exception on your own.
Therefore in Bitdefender, you go to protection> online security> exceptions
Here you can either enter the name of the NAS (NAS326, NAS540 or NAS542) or the IP address of the NAS:
Now you can access the NAS again.
For other AV-solutions, you need to have a look in the manual or contact the respective support.