I am glad that you finally understand to use a coupling capacitor to block DC but pass the AC.
In the datasheet of the LM3915 there are good peak detectors shown. They charge the timing capacitor very quickly from a low source resistance so that short duration peaks can be seen. They discharge the capacitor slowly (about 30ms) so that our slow vision can see them.
Your circuit has the capacitor charging fairly slowly through high value resistors and has it discharging very quickly since the capacitor value is too low and the 270k resistor to ground on the input of the LM3915 should be 1M as shown in the datasheet.