My husband is having the same issue with his S8.
We purchased the phone at Best Buy 5/12/2017. He just started having the charging problem in late July. I have emailed Samsung and I am waiting for a response. Like others, here are some of the issues I am seeing and what we've done to try and resolve it.
-Fast-charging not working
-Phone charging extremely slow and displays that the remaining charging time is up to 20 HOURS
-Leave phone plugged in overnight and only get up to ~35% charged
-Receive notification stating to check the connection of the charger.
-Only using the charger that came with the phone
-Blown out ports with air
-Swabbed port with rubbing alcohol and dried
-Disabled and Re-enabled Fast Cable Charging
-Powered on/off device
-Completed a factory reset
-Sometimes when I flip the plug over it works like normal, but not always
I had a similar problem when i used a micro-usb with the adapter. When I left my phone case on and plugged it in my phoned it would not charge correctly. So I would try taking the case off than plugging it in. When I had the case on it seemed to be seatted correctly, but no. I hope helps. This was also the case with my OTG adapter. So yeah try without the case on.
Just an FYI, I've figured out the issue for my phone at least. It's not the phone, it's the charging cord that came with the phone. I use the USB-C adapter that came with the phone and it charges and connects perfectly with my old charging cord. Also, I purchased a car charger (Belkin) and that cord works as well with the phone, wall adapter, in the car and with my Mophie.
I've noticed this issue as well. I'd say mine started on and off about 2 1/2 weeks ago but has been really consistent for the last week or so. I've only used the cable given with the phone, and have plugged that into the provided block, my car usb and a usb charger in a surge protector at work.
Sometimes the issue will be fixed by rotating the charger in the extension cord I have (trying in the different ports and switching which way the prongs for in) or rotating the usb-c side of the cord, but no luck tonight. I've tried blowing in the ports as well. I got the phone the day it came out if that helps. My service provider is Verizon.
When I first got it didn't do it. About a week later, "incomplete connection. I'm using the wall charger that came with the phone.
The funny thing is that it came with an adaptor to convert a regular usb to charge the S8. I don't have the problem with the adaptor.
SOLUTIONS I'VE TRIED
- Make sure all my connections were tight
- turned the phone off and back on