Can you provide any additional information about your account that might be relevant: (A link to your non-private steam profile might be helpful.) You say your main account does not work in Miranda, but your other account does? What are the main differences between those accounts? Did you do stuff like re-check your login info entered into Miranda? Generally when connecting from a new machine/device with Steam Guard on you should get sent an email with a code to verify your login, are you getting this email / are you entering this information / are you seeing the password popup. Do you use any special ascii characters in your username or password or anything like that? Might be helpful to know some of these things to try and help solve the issue or figure out whats going on.
Edit: Also knowing which version of Miranda you're running as well as if you're using any other plugins would potentially be good too. Really old versions of Miranda had problems with steam accounts set to use Steam's Mobile Authenticator for example, but worked fine for Steam Guard accounts. (For versions that are over a year old anyway.)
Edit 2: I do experience an occasional issue where Miranda will say its connecting to Steam, but never actually connect. Im not sure if this is related to the Steam community servers being down (as usually i can log into the steam client just fine, but not Miranda) or if its some kind of bug in Miranda. To fix this usually i have to close Miranda and wait a few minutes so that any failed connection attempts have timed out, then open it again. --- The former 'bug' also often leads to an issue with the Steam protocol where if you log off and back on very quickly, sometimes Miranda will say you're online, but all of your contacts will still show as offline, yet some of them might have game symbols next to them. What I believe is happening is that Steam probably only sends Miranda a full contact list status update every so often, if you've already gotten one recently, Steam will only send updates to you when a contact changes their status (logs on / idles / starts a new game.) thus causing everyone to show as offline except anyone who has changed since. Logging off and then back on after 2-5 minutes will usually fix this, but sometimes I close the client anyway just to make sure its not some kind of memory leak.
- What do you mean non-private? That being private might be a problem for Miranda? Actually I did set my account as private, but I tried now to revert it to public and the login didn't work anyway
- The account where I can login is a brand new one, even though I can't add anyone since I didn't use any money in it, it can still be shown as "online", something that doesn't happen with my main account (there is the icon where the circle is loading, and it's stuck in that state)
- I'm always using latest miranda + plugin nightly versions
- I tried both with steam guard enabled and disabled. When this problem started, steam guard was enabled, and previously I would receive sometimes captcha codes (only once in a while, I don't know the reason for this) but once inserted I could login fine. Not anymore, and no error popups
- No special characters in the password, it's just a long one. But the problem started when the password was much simpler, changing it didn't resolve
- I remember the offline contacts problem, happened from time to time. Trying to login again just fixed it most of the times. On the other hand my account problem has 0% chance of success in login, but I can login with different programs (see previous post)