Hello
Generate the sha1 and place in your google firebase console project
http://prntscr.com/r06dg5 and then download the google.service.json file reverse this
http://prntscr.com/r06f0p
ionic Cordova plugin add
[email protected] --variable REVERSED_CLIENT_ID=com.googleusercontent.apps.sa4eup240iae2sac48kcmkb623jp0g4v-619318875199
Place the reverse client id in the google plugin login command
http://prntscr.com/r06g60
ionic cordova build --release android
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore wplms.keystore app.aab wplms
C:\Users\99fus\AppData\Local\Android\Sdk\build-tools\29.0.2\zipalign.exe -v 4 app-release-unsigned.apk wplms.apk
Follow the above doc for adding the google login.