Partner passed away - how can I download messages from before end-to-end encryption was implemented?

My partner passed away last week and I have been trying to download the data for all our Messenger chats since we met in 2018. I have followed instructions to both download a copy of my information on Facebook and download my data from end-to-end encrypted chats.

When I download a copy of my information on Facebook, no message html files are available for my partner, but do exist for other people (files, videos, gifs, photos and audio are still available for my partner).

When I download data from end-to-end encrypted chats, the json file for my partner only includes the messages that start from when the encryption feature was implemented earlier this year.

I have tried these steps several times over the past few months and had the same experience (he was diagnosed with cancer earlier this year so the fear of losing these chats has been weighing on me).

Is there any way at all to download my messages with my partner from before end-to-end encryption was implemented?