Pb is a warning that there is no water flowing through the Enviroswim system.  If there is no water flow it will most likely be an issue with your pump or valve settings, not an issue with Enviroswim.

If there is water flowing through the system then the issues could be a loose or broken connection on the oxidiser cable connections (small white wire connection to the flow sensor). This applies to cell plates on pre Nov 2014 systems only. Post Nov 14 systems have hard wired and sealed connections so the system may require returning to us or an authorized repairer for inspection.