Recently purchased MTS275 Lightning and am having trouble getting tig to arc.
I've been welding for over 35 years, mostly mig, spool gun and stick but very little tig experience.

I've tried both the foot pedal and the thumb switch.
I also tried HF and lift start. I do get an arc once in a while but it melts the tungsten and then doesn't continue arc.
I also tried manual and power set modes.
Would it be that I have a defective welder or am I doing something wrong? Parameters? Trying to tig aluminum at this point.
Any tips would be appreciated.