Could be that the gas itself was bad – ethanol phase separation so that there was water in the gas.
Could it also be that his mix was a little off?
Amsoil is very thick and if the entire amount didn’t get in the gas, or it was measured wrong from a larger container, or was poured in an empty gas can and not mixed well – 80:1 could easily become over 100:1.
Another thing to consider is the use of fuel additives/stabilizers. Stabilizers are more of a “fuel” than an “oil” and too much stabilizer will dilute your gas/oil mix.
Good to hear that he got it running again, and thanks for the update.