How to Download End-to-End Encrypted Messenger Messages from Facebook?

Step 1. Open and log into your facebook account. Click your profile photo in the bottom left corner.
Step 2. Click Privacy & safety.
Step 3. Click End-to-end encrypted chats.

Check Secure storage status:
If Secure storage is ON, click on it and go to section 4.
If Secure storage is OFF, go to section 3.
Check Secure storage status
How to turn on Secure storage?
Step 1. If Secure storage is Off, click on it.
Step 2. Click Turn on Secure storage.
Step 3. Choose a secure storage option. You can choose a PIN or a 40-character code.
Step 4. Follow the on-screen instructions to create a PIN or copy a 40-character code. Remember to save your PIN or code somewhere safe.
After turning 'Secure storage' on, repeat steps in section 1 and section 2 then go to section 4.

Note: After turning 'Secure storage' on, you may need to re-enter your login information for in order to access the secure storage feature.
Step 1. Click Secure storage.
Step 2. Click Download secure storage data.
Step 3. Click Download file button and enter your Facebook password when prompted.
Step 4. Click Download button. It may take several minutes to prepare your download file.

Note: All of your end-to-end encrypted messages and attachments will be formatted into a ZIP file.
Tansee iPhone Message Transfer or Tansee Android Message Transfer can extract the zip file(s) downloaded from Facebook.
Tansee can be used to save all Facebook Messenger messages, including all attachments, as PDF files.
After downloading the zip file(s) from Facebook, please download and install the latest version of Tansee iPhone Message Transfer here.
Alternatively, you can download and install the latest version of Tansee Android Message Transfer here.
1. Open either Tansee iPhone Message Transfer or Tansee Android Message Transfer.
2. Click on the 'Read Messenger Messages' option.
3. Select the zip file that contains your Facebook messages.
4. Click on 'Read zip files' and Tansee will automatically extract and display all of your messages.
5. Once Tansee has finished reading all of your messages, click on the save button and select the PDF file format.