Avoid downloading .rar or .zip files from unverified third-party blogs or forums. These files can contain malware or incorrect firmware that may permanently "brick" (disable) your device.
If you are comfortable sharing, what is your device currently on? This can help in finding the correct official firmware version.
: Go to Settings > General management > Reset > Reset network settings .
: If software resets and official firmware do not fix the issue, it may be a physical problem with the baseband IC on the motherboard, which often requires professional repair like "reballing".