One of the main reasons I wanted Logi Options+ with the MX Master 3S for Mac was for the button customisation. The mouse works fine as a normal mouse without it, but Logi Options+ is what makes the extra buttons useful.
The problem I had was that the mouse was connected over Bluetooth and worked normally in macOS, but it would not show up in the Logi Options+ UI.
In my case this was not really a Bluetooth problem. Logi Options+ had already detected the mouse internally. The problem was that it had not been marked as onboarded in the UI config.
If the mouse is not working in macOS at all, this is a different problem. This post is for the case where the mouse works normally in macOS but still does not appear in Logi Options+.
The useful files were:
~/Library/Application\ Support/logioptionsplus/devio_cache/paired.xml ~/Library/Application\ Support/logioptionsplus/settings.db ~/Library/Application\ Support/logioptionsplus/config.json
In paired.xml the mouse was already present:
<device path="C1840740-5F9E-D02E-C070-02853AC9AE25" pid="B034" name="MX Master 3S M" serial="E3C68ECB"/>
settings.db also contained it. This is the query I used:
sqlite3 ~/Library/Application\ Support/logioptionsplus/settings.db <<'SQL' .mode line select json_extract(cast(file as text), '$.ever_connected_devices') as ever_connected_devices from data where _id = 1; SQL
In my case that showed:
"deviceModel":"2b034_ext4" "deviceType":"MOUSE" "slotPrefix":"mx-master-3s-2b034"
The important part there is the model. For me it was 2b034_ext4, so the model ID I needed was 2b034.
The actual problem was in config.json. Mine contained:
"onboardedDevices": []
That was the issue.
The mouse had already been detected, but the UI had no onboarded devices listed, so Logi Options+ behaved as if nothing supported was connected.
The fix was to change this:
"onboardedDevices": []
to this:
"onboardedDevices": [ "2b034" ]
Then quit and reopen Logi Options+.
That was enough to make the mouse appear in the UI again.
I also reinstalled Logi Options+ and reproduced the same problem again. After reinstalling, the mouse still showed up in paired.xml and settings.db, but onboardedDevices was still empty. Adding 2b034 fixed it again.
This assumes the normal permissions and Logitech driver extension are already in place. In my case those mattered, but they were not the thing that fixed the mouse not showing up in the UI.