I realized today that I haven't had my sell boost activate from either my peacock or my squirrel in quite a while; definitely not within the timeframe that I can see in my activity log while playing in my browser (running Arie's Mod and have kept up with updates, in case that's important) and I think it goes back to when I got my capybara and added them to my "sell team", although I have no actual records to determine when my last sell boost was or when I got the capybara so that's purely conjecture/determined likely based on vague memories on my part.
The capybara refunds crops almost every time I sell crops, but I haven't gotten a single sell boost in at least the last week (but I'm pretty sure it's been longer). I initially thought it might be related to having the capybara deployed, so I removed him from the team and tried with another squirrel in their place (along with the first squirrel and peacock that were already deployed) but I still haven't gotten a sell boost after selling almost an entire garden worth of crops (which previously would've resulted in 2-3 activations of the ability).
I'm planning to check it out in Discord rather than through the browser to see if that has any impact, but I wanted to post it here in case it's a bug and/or see if anyone else is having the same issue.