I have read and tried all of the help tips to get the bowl to flush on the "first" flush to no avail.
Cleaned all the jets and the siphon port, were not to bad at all. This toilet is probably about 4 years old, have checked the water level in the tank, it's fine.
I get "bubbles" on the first flush but not so many on the second and successful flush. Could a leaking, air only? Seal cause the problem? There is no sign of water escaping from the seal. Getting a little flustrated :):) :(

This can be caused by a vent stack that is clogging up. Best bet is to snake the vent from the roof with a sewer rodder long enough to reach roof to basement plus 20'. Just noticed you aren't the only one with this issue and Tom is looking toward the same fix as me. https://www.askmehelpdesk.com/plumbi...ns-414205.html

I climber on the roof yesterday, put a hose in the vent ad put at least 30-40 gallons of water down the vent pipe. Guess what, no difference. If anything it may be a bit slower on the "second" flush now. Bought ready to call a drain guy, I don't have a 40' snake and really do not like the peak of the roof :):)

Flussed,

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I climber on the roof yesterday, put a hose in the vent ad put at least 30-40 gallons of water down the vent pipe. Guess what, no difference.

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You don't understand the natureof a partial blockage. A partial blockage will allow liquid to pass as lone as the volume holds steady. Like running a hose down a vent.
Your toilet doesn't meter water out of a 3/4 ir 1/2" hose. It lets go with a 2 5/8ths inch blast of 3.5 or 1.6 (in the case of a new toilet) gallons of water all at once.
This volune of water will hit a partial clog in the drain and bounce back for a instant and sending back pressure back uo to the bowl. This back pressuire is what stops the siphon action of a good solid flush. You have a partial blockage in your drain line . This is nbest reached by pulling the bowl and snaking from the toilet flange.
However if you go down the lavatory roof vent put out enough snake to reach the base and 20 feet more. Good luck, Tom