This could be caused if the speaker is not connected to the power source or if the fuse is blown.

To remedy this, try connecting the speaker to a known working AC power source or check the fuse. If the fuse is blown, replace it with the spare provided in the fuse holder in the IEC power connector. If the speaker still fails to power on, please call JBL Customer Service.

This troubleshooting item can also be found in Appendix F of the Owner's Manual for the LSR4326p and LSR4328p.