If you cannot do that, switch to Airplane Mode and back so that the phone is registered on the network again and that might resolve any network issue that could be causing iMessage not working on iPhone 13. If you are using cellular data right now, switch to Wi-Fi and check again. At one time, there can only be one line selected. If you are having another line active, check that the line you want to use is selected. Take note that your iPhone is a dual-SIM phone. If you see a checkmark already, tap it to remove the checkmark and tap it again after a few seconds to re-register the number for iMessage. Check the email and phone number you wish to receive and reply from. Step 3: There are two sections here, the first section deals with sending and receiving. There should be a checkmark next to it if it is. While it is supposed to work with your Apple ID alone, it may help to ensure that the cell number is active, too. iMessage uses your iCloud ID or Apple ID and your cellphone number. Now, even though iMessage is activated, it might not be set up correctly for you. Solution 3: Is iMessage Set Up Correctly? Try again after 24 hours to see if it gets activated. The same holds true if you got a SIM change done, including if you upgraded your regular SIM to eSIM. If you recently switched providers, it is possible that you are under a 24-hour cooling period wherein SMS is disabled on your line. This might seem absurd to you, but under some circumstances, SMS service may be currently non-functional on your iPhone, and activating iMessage requires SMS service even if you never see it. Problem solved! However, if iMessage does not activate, this might point to another issue. If iMessage activates successfully, you should be able to send and receive iMessage from now on. Wait a few seconds and toggle it back on. Step 2: If iMessage is toggled on, toggle it off. Step 1: Go to Settings and scroll down and tap Messages The first thing and the easiest of all is to activate iMessage again. IMessage needs to be enabled for it to work, and it is possible that it is disabled or not working for some reason. Here are simple fixes to the iMessage not working issue on your new iPhone 13. iMessage requires enabling, and that itself requires a couple of other things. Now that you know the issue is somewhere between your iPhone and Apple, there are a few things you can do to check where the iMessage not working issue exists. Part II: 9 Simple Ways to Fix iMessage Not Working on iPhone 13(including Dr.Fone - System Repair (iOS))