ALT 3 is the TX PLL unlock alarm. Check your TX frequency and make sure you're not outside the frequency range of the repeater. If you're within the frequency range, it's possible that you goofed with adjustment settings or the TX PLL/VCO circuit isn't working properly.
Most often, it's a simple problem of trying to TX or RX out of band. The PLL circuit can't lock onto the frequency, so it remains "unlocked".
Repeater Icom FR4000
Linear Mode
