That looks to be an LG HG2 20A battery and even if it is an authentic, you are pushing its limits if approaching 60 watts on any single 18650 mod. As it drains, the battery is less likely to be able to provide enough power to provide the wattage requested. Just as a test, when it says "check battery", try turning down the watts by 20 or so and see if it fires then. To be clear, I am not suggesting this as a regular solution! If you are running it at or under 35 watts, I would be more inclined to think you have something other then an authentic LG or they accidently gave you an older battery. You might take it back to the shop and ask them to check it for you.
It may just be the nature of the beast, battery life on a single 18650 mod running at 50+ watts. I like my AL85, but due to the tank size and limited battery life, it is only used at home or on short trips out. Otherwise, I go with a dual 18650 mod. Besides checking in with the shop you got it from, the only other solution might be to buy another battery (maybe even a 25amp, but giving up mah rating) from an authorized seller and see if it lasts longer. Even if it doesn't, get a carrying case with it so you can carry it to switch out when needed.
If you want to extend battery life a bit, shorten the screen timeout and lower the contrast a bit. I have screen time at 30 seconds and contrast a 70%.....don't remember what factory settings were. I am testing mine right now with a T8 coil (0.15Ω) at 54 watts with a 1 year old LG HG2 battery showing just under 50% (keep in mind, that is just a gauge) and amps showing at 17 to 18 and it is still firing. But I expect the "check battery" message at any time now.
IMHO, if you are running the tank at 50+ watts, see if the shop will swap it out for a dual 18650 mod and you should be good to go. I prefer carrying that extra battery in a mod rather then a protective case.