Hi, along with the steps given above you can also perform Reset Network settings on the device and check for the issue.
Go to Settings, and then select General management >> Find and select Reset >> Choose Reset network settings >> Tap on the Reset settings button >> Tap on the Reset button.
Note: When you reset the network settings, the Wi-Fi and Bluetooth information connection are reset.
Please check if your SIM card is placed correctly. Sometimes, it might get loose or fall out of its slot, so ensure it's in place properly.
If that doesn't work, try replacing your SIM card.
