Invalid IMEI after Rooted of Flashed your Android, read this guide to fix it in 1 minute !
Step 1: Root your Mobile
Step 2: Download Chamelephon on Google App: https://play.google.com/store/apps/details?id=com.cryptotel.chamelephon
Note: Mediatek 65XX devices supported only
Step 3: Run Chamelephon
Step 4: Generate random IMEIs
Step 5: Apply new IMEIs
After that turn off your mobile (or remove your battery) then remove your SIM cards and clean it. Final, switch SIM1 slot to SIM2 and Reboot your Mobile.