Agreed about getting the user's manual and, hopefully, the pickling solution has not leaked out and is still effective. Install new filter elements. Check that the pumps run, sea strainer is clear, seacock is open, selector valve at "bypass" or "sample". Run the lift pump for 10 minutes and verify that the bypass water is discharging overboard. Switch on the high pressure pump, gently increase the pressure to around 800 psi and let it run for 30 minutes. It should now be making fresh-tasting water at slightly less than the rated output. If it doesn't make fresh water, or very little, your membrane is probably toast and a new one may be the only solution.
When you have the bugs ironed out, I suggest running the system for 10 minutes every week or so using only the fresh water flush system and at very low pressure. This keeps the pumps and valves exercised and flushes the membrane. It also avoids dirtying the filters and makes distilled water for topping up the batteries.
