Remeha avanta plus

[scimbo]

I have a remeha avanta plus that was installed 3 years ago. Has anyone had problems with pressure valves needing replacing. My system shows low pressure (0.7bar) and when opening the feed tap, the pressure does not increase. I have bled the air out of the system (there was a significant amount) but still the pressure will not rise and the heating seems to be working fine.