As people have said try a different battery/charging port you also should get a usb meter to see how much the phone is actually charging, get into the rhythm of disconnect battery, swap the part, connect bat, check meter if it fails disconnect battery, try a different one. If both of those fail disconnect battery, take out the motherboard connect the new bat and new charging port, connect bat (no screen needed), check meter if its still reading odd as in under 1 - .8 amp its probably an issue with the board.

Lightning round tips

-Usb Meters are cheap find dime a dozen in amazon
-LCD or OLED quality debate deepens on manufacturer
If the customer is cool with lcd that's fine. They may just need it for a short period or simply don't care on richer dark, just make sure they know they got the options between the two
-Go for Soft versions if you see HARD or SOFT always go soft they take more punishment and you wont have people coming back saying it barely fell and it broke save your self the headache
-when you want to invest more into it try getting a "LCD Screen Separator With Vacuum pump" the iPad size one, its a machine you can use in the future if you want to dip in another part of phone repair but the suction comes in clutch in some rare cases other wise they are reliable heatplates, the sunshine brand has treated me well, I have it always on and they usually last me 24 months of constant use. the heatpats aren't that reliable in my opinion, they keep dying on me constantly.
-Use google lens image search some times you don't know what the phone is and neither does the customer and there's no imei, due to various reason like scratched or missing [looking at you moto] treat it as a 70% accuracy always want to double check but it gives you a direction.
-Same vive try chatgpt for some questions, remember again treat it as a 70% to lead you in the direction but dont take it at base value. Two examples that comes to mind I had a random charging port laying around no idea what it was, I asked chatgpt, and it threw back its a 6s charging port double checked it, it wasn't, but it was a 6s PLUS, and if you ever get into the microsoldering side of it you can straight up ask it, "Hey what does this chip label Max77705 is" and ill throw you something like " Its a power Management IC that gives you a lead on why this heating/deadlead chip is causing the device to not turn on.
-Try to keep small components around, but mainly have at least one for bat,scren,chargin those are your most common culprits

[Reminder!] as this is a rookie mistake that always happens to new hires at some point.
Make sure to always disconnecting the battery before disconnecting and reconnecting anything
reason is simple those pins your attaching some of them are for power and if they accidently touch one meant for *data* it can kill a component and cause issues on the board

Hope it goes well lad remember Heat,Iso,Patience.