The max amp draw for that amp is 110 amps, a power supply for max power out for the amp. To run it on SSB is an option.
The amp is a class C amp, meaning it's not made for SSB use unless it has the option.
The AM carrier keeps the amp keyed as long as you put enough power into it to keep it keyed while you talk.
If you are trying to use it on SSB then as you talk the relay in the amp will chatter as you talk, because there is no carrier on SSB, unless you have the SSB option.
If there is another problem you will have to explain it in more detail.
How long is the jumper cable between the radio and the amp? There have been problems that other people have had with amps that a longer jumper has made the difference.
The one thing you state is that the max power output is 500 watts or so, is that average or PEP? If it's average you would see a bigger swing