Leasure battery?

Leasure battery 4yrs old and car & leasure battery charger which has panel lights indicating rate of charge.
Problem:
Panel lights failed to illuminate when leasure battery connected and charger info states don't use check terminal posts are clean....Yes. Check lead are not broken....No fault, they're ok with current proved at charger leads end using a neon car wiring tester and Budgie mains tester run down the cables and was also sensitive enough to pick up current running down the battery connection leads.

Battery is in low state of charge, is it possible a fault in the battery cells are interupting the charge current so not illuminating the charger panel lights?.
The battery is a sealed battery so cell electrolyte cannot be tested.