EDIT: Ran into my first "daily limit exceeded for this account" or whatever message today, and, honestly, at first, I was pissed BUT! I read the reviews and one review in particular had instructions which helped even though it was a somewhat involved process, so I will copy and paste it here if anyone running into the same issue has the patience to try to resolve it as intended:

"
Rated 5 out of 5
by Ling Ling From QLD, a year ago
A lot of people are having trouble setting up the account here is how to do it.
1. Go to https://console.acrcloud.com
2. Create an account.
3. Select your geographical region
2. Click 'Audio & Video Recognition' then 'Projects'.
3. Select 'Audio & Video Recognition' again and click 'Create Project'.
4. Any name will do, select 'Recorded Audio' and 'ACRCloud Music' as the bucket, allow all 3rd party integration.
5. After creating project there will be 3 text strings to copy into the options portion of the Song ID extension. Copy the 'Host', 'access key' and 'secret key' to the corresponding entries.
6. If the project 'Status Check' is 2/2 with a tick mark next to it you have done everything correctly.

You DO NOT need to create a custom bucket for Song ID to work.
"

In Firefox at least, the unique 'host', 'access key' and 'secret keys' are to be manually entered into the app's 'manage extensions' page under the 'preferences' tab. After having done that, the problem was completely solved for me. Solid app, and great work!

My original review ~2017:
Just installed. Runs beautifully in Firefox Quantum for (K)ubuntu so far. Comes up with a match almost every time I've used it so far, and correctly (as far as I've been able to tell), even with reasonably new tunes. Keep up the good work!