Google is excelling again - as the whole “uncensored” Big-Tech IT now.
The short summary is that for nearly a year, Google was hiding Proton Mail from search results for queries such as ‘secure email’ and ‘encrypted email’. This was highly suspicious because Proton Mail has long been the world’s largest encrypted email provider.
I had a similar issue, but I google searched and found a setting I had to redo or change and it’s worked fine since then. Afraid I don’t remember what I had done. It was like a month ago and late, but it’s been problem free for me.