You might want to make sure apps are closed before you charge it. Sometimes you could have 2-3 apps running in the background & that will keep it from charging. Mine use to always say weak charge, then I found out Chrome never closed & it kept running in the background.
Mine is doing the same thing literally my phone has been on the charger all evening and it's only at 18% now I have try to optimize it and it did nothing to it I'm o. A galaxy j7 what eles could I do
I have the Galaxy s8+ too. Mine started failing a few days ago at charging. I've stopped all the background apps, I've optimized with some thingy to click on that frees up something. The phone came with two charging things. I have the cord, I have the little piece that fits into the phone, but did a male to male thing come with the phone that inserts into that second non-cord charging thing?
I just got a fake new cord. It fits more snuggly like the original cord fit.
my phone is charging better than it did before the new cord.
This doesn't explain why the phone would not hold a charge however as of a few days ago.