Login Error: There is an error in logging you into this application. Please try again later

The error occurs because of invalid hash key.

We can create Hash key using the below command and update the same here under Settings-> Basic -> Android HashKeys

keytool -exportcert -alias ADD_RELEASE_KEY_ALIASE_HERE -keystore ADD_UR_KEYSTORE_PATH_HERE | openssl sha1 -binary | openssl base64

You can find the Relase Key Alias of your keystore using the below command if needed:

keytool -list -keystore ADD_UR_KEYSTORE_PATH_HERE

I have also experience an issue like by using the above HashKey the login works fine if I install the release APK directly to the device, But when I upload the APK to Play Store and install app from store then it shows the same Login failed error. The fix for this is as follows:

1. Go to Release Management here

2. Select Release Management → App Signing

3. You can see SHA1 key in hex format App signing certificate.

4. Copy the SHA1 in hex format and convert it in to base64 format, you can use this link do that without the SHA1: part of the hex.

5. Go to Facebook developer console and add the key (after convert to base 64) in the 

   settings → basic → key hashes

ANSWER

Just throwing this out there for people still experiencing this issue.The hash I created through the keytool was somehow incorrect. I fixed it by doing the following:

If you already uploaded your app to the playstore and enabled "app signing by Google Play" there is a solution (at least this worked for me):

1. Login into the Google Play Console
2. Click on the app you want the hash from
3. Now, open the navigation on the left hand side
4. Under Release click Setup > App integrity
5. Under App signing certificate copy the SHA-1 certificate fingerprint
6. Go to http://tomeko.net/online_tools/hex_to_base64.php
7. Paste the SHA-1 in the first field
8. Copy the text in input field under Output (base64)
9. Now open developer.facebook.com/apps
10. Navigate to the dashboard of your app (My Apps > Your App Name)
11. On the left side navigate to Settings > Basic
12. Paste the Base64 text here under Key Hashes

That should fix the issue.

UPDATE

The steps above should still fully work.

But if you do not want to paste your key on that website, here is an alternative to step 6,7,8 below:

here's a oneliner Node.js command to do the same:

node -e 'console.log(Buffer.from(process.argv[1].split(":").map(hex => parseInt(hex, 16))).toString("base64"))' '5E:8F:16:06:2E:A3:CD:2C:4A:0D:54:78:76:BA:A6:F3:8C:AB:F6:25'

credits: mifi

I also Face this problem .Update your key hash on Facebook