SOS Confused

So my 99 Sport had been running good without issues until about an hour ago.
My wife went to move the Jeep and she said it just clicked.
Went out and checked it out and sure enough it just clicked.
So being as the interior lights were dim I figured battery, jumped it and after a couple of minutes it ran but interior lights were flickering. The flickering went away and they stayed nice and bright. I took it around and the Check Gauges light came on and I noticed that the volts were at 19.
Got home, turned off the Jeep and tried to start it again, lights were dim and then click.
I pulled out a voltage meter and the battery read 12.6. I opened the driver door and noticed that the lights were still dim.
I have checked all my connections, battery, alternator, starter etc and all are good.
I went back to see if it started up and click.
As you can see I am way to confused to even start with a possible solution.
I have 12.6 on the batt, but the interior lights make it look like I have 3 volts, and then there is the click not to mention the 19 volt reading.

Any help would be greatly appreciated as this is our only vehicle.

Sounds like a bad battery, alternator, or both.

ground straps are notorious. i had a bad battery to body ground. would do the same thing if it was connected. try disconnecting that ground and see what you get, and if that doesnt work clean up both sides of the connection, and/or replace cable. lmk, ill be following this post

If it's the alternator, I think you'd have dropping voltage and the lights, though they'd grow dim, would not likely flicker. IN addition, once charged, a good battery should stay all right for the night, and not be dead again in the morning. So I'd recheck the connections, making sure all grounds are good, and no corrosion in hidden places. Nice shiny battery terminals and all. And then get the battery tested.

I have had a couple of brush failures on high mileage XJ alternators. When this happens on 97-01, you lose charge intermittently at first, then for longer periods. The voltage drops, and after a short while the voltmeter drops to zero and sets the "check gauges" light. If it's that, you should be able, while the engine is running, to tap the alternator with a stick or something, and get the brushes to make contact again for a while. You'll both see and hear the change immediately if this happens, and if that is the case, then your alternator needs new brushes (or replacement).

Same situation for me about a month ago...

12.5 - 12.7 VOLTS

Took it down and had it load tested...battery was shot (yeah, I know...even with 12.6 volts)

i'd take the alternator to be tested, at a dedicated automotive electric shop... while alts out, if u have a battery charger, charge the battery, if not bring the battery along with alternator to the shop to be tested... before re-installing, dont just look at the connections, literally take them off their mounts (to double check the terminal itself hasnt separated from the wire), clean the terminals & surface they mount to with a steel/brass brush... also get the code read (for free) at AZ/AA (also u could rent the tester, since obviously wont be able to bring the XJ there)... the computer is trying to tell u something with the "check engine" light (CEL)

once all that's been eliminated, and if problem still exists, could be either starter motor or solenoid... but by the "dim lights" symptom, i'd assume the alternator is not charging the battery since when jumped, it runs

EDIT: just re-read original post & realized u said "check gauges"... combined with the other symptoms, i'm 99.9999% sure its the alternator... i had the almost the same thing... engine running, verified with a meter, i had 20V at the battery, 19 at the dash gauge, & "Check Gauges"... it was the alternator