Otii not connecting on Catalina 10.15.3

Hi everyone,

I just got an Otii and when I try to start a new project and connect the Otii I get a message ‘Connect your tool!’ and the Otii makes a clicking sound for a while. I am running the software on MacOS Catalina 10.15.3 on my 15 inch 2018 Macbook pro.

When I boot into Windows the Otii connects and everything works fine, so it’s not a hardware issue. I’m logged in on the app and I’ve updated to the latest firmware (using Windows) but the MacOS app still doesn’t connect. Also, when I start a tcp server from preferences and run an example python script I get ‘No Arc connected!’ log. Any suggestions?


I got it to work when I connected 9V power adapter to the Otii. It is weird that it doesn’t work just on USB power on MacOS (I’ve updated to latest 10.15.4 too) especially given that it works on Windows on the same device.

Hi Leszek and welcome to the forum.

Thank you for reporting this and sorry for late reply.
We will look into this, perhaps there is some timing issue.

Best regards,

1 Like

Same problem here on Mac mini (OS 10.15.7) - but an external power supply does not help. Some UART were recognized (Bluetooth and LG Monitor) which I blacklisted. Tried to un-blacklist these and start over - but still doesn’t work. No Windows PC in sight either so we are at a standstill.

Hi and welcome to the forum.

Could you create a case in our case system and I’ll dig deeper into this issue.

Best regards,

I already did that before posting in the forum


Loose / bad USB connector on Arc unit. Intermittent connection, so must be careful to not move/touch the Arc lest it become disconnected. :unamused:
The supplied USB cable does not seem to work so needed to find my own. USB cables … isn’t there anything better?

The issue mentioned in the messages above from April is not the same as the one stated by @digitld . We are grateful for @digitld highlighting the issue with Otii Arc not starting with the cable received in the package, and helping us figure out what was wrong. See here a message on what happened.

Thanks, The Qoitech Team.