S21 won’t charge

Mizzkill you might want to try a wireless charger. Also make sure you are using Samsung branded chargers and cords to ensure proper charge. 

Brendizzzy's suggestion for wireless charging is great! You might also consider cleaning out the charging port really well. My husband has a Samsung phone and has to clean the port every few months. Last time we took it to the Geek Squad counter at BestBuy and they cleaned it out for us. It took 5 minutes and they didn't charge us a cent. 

Thank you guys!  I have cleaned out the port several times.  The wireless charger works, but they are also slow charging.  The wireless charger I have is from Amazon so it may not be the best. This is actually my husband's phone so I am sure that the port is getting dirty.  He told me that he had to squeeze the charger (the metal part that actually goes into the port) to get it to work, but it will disconnect a lot.  I may take it to Best Buy and see if they can help.  I looked into how to change the port ourselves, but it looks too tedious for me.  lol

Since it is slow charging on the wireless pad, too, it could be more than a dirty port. Getting it cleaned out properly is still a good idea, but I would also look a little deeper into what the phone is doing. 

• Did it start having charging issues after an app or software update that you know of? It could be that the update is not sitting right or that an update is needed and hasn't been done. 
• Do you use any third-party battery saver or task manager apps? If so, uninstall those please.
• Go into settings and select Battery. This should show a list of apps and how much battery they are using. Pay attention to any that are using a lot and possibly update or uninstall. 
• A good maintenance item is to Limpiar la partición de la caché. 
• Also close out of all recent apps before plugging in to make sure nothing is trying to run in the background. 

Over time, the things that we add to our phone can start to "stack" in an inefficient way. Think of the phone as a box and all your apps as nick-nacks. You get a new thing and put it in a free space in the box. For the most part, things go well, and everything fits. There are spots where there is extra free space and where things are stacked in an awkward way. Eventually, you need to empty the box and restack everything in a better way, so everything sits right. That would be a master reset. It seems like a drastic step, but it can help to make sure that the phone and all the cool stuff you do on it is working smoothly and not trying too hard to run or stay charged. 

Is adaptive charging turned on in the settings?