Yes, people do know (or no) what the error code is. So could you, with a quick Google search.
Just do a Google search for - say - "isar he30 boiler fault 3 lines" and you will find results like this, which suggest what may be wrong and things you can (and can't) do about it.
https://www.diynot.com/diy/threads/ideal-isar-he35-3-line-fault.300003/
acp, July 2017
