I had the same error, it prompted me to look at the source code and try to fix this.
I refactored several parts of this app (still WIP) and found that it will work when the focusing is set to DMF or MF, also it works in all modes when I added a shutter half-press before trying to take the pictures.
My WIP branch: https://github.com/hameno/timelapse-sony/tree/ilce_7m3

Thank you, @hameno ! This is exactly what we need. How do I install your branch on my Nexus 6P?

Only way currently is to check it out locally and build the apk using gradle (./gradlew assembleDebug)

Hmm. I'm not familiar with the process to do that. Do I need to install Android Studio and everything?

You would need to install the SDK, yes. IDE is not necessary if you only want to build the apk.
But I can try to find some time to build it tomorrow and provide an apk.

That would be amazing. I'm sure all a7iii owners out there would be super appreciative!

Thank you @hameno for your amazing work.
Did you plan to do a pull request soon? After some verifications/tests I can plan to include your work directly in the app published in the play store.

I wasn't sure if you'd welcome such a large change. It's basically a complete rewrite and conversion to Kotlin. But if you'd like, I can of course create a PR :)

Here you go #41

@brianrc I've created a debug apk for you to test: https://cloud.psdev.de/s/kGxpRp5SmzcXwFR

I just tested it out and unfortunately it's not really working for me despite my tries at playing with different settings.

It's weird, after accepting some access permissions, it connected ok the first time, but each time after the program never gets beyond the 'Wifi connection' step.

Here are the steps I took:
I uninstalled the Timelapse app, then installed the apk.

On my A7III I selected 'Ctrl w/ Smartphone' and turned it on and set 'Always Connected' to 'On.' Then went to 'Connection' and started up that process.

On the Phone I went into the app, Wifi enabled shows a checkmark, but Wifi connection just keeps spinning. 'Sony API connection' shows a red X.

I've tried restarting the app and restarting the camera multiple times. Wifi connection just keeps on spinning.

My Nexus 6P is running Android version 8.0.0.

Is there anything I'm missing?

@brianrc Sounds like you did not setup the wifi connection yet. Try holding your phone to the side of the camera where the SD cards are. It will setup the wifi connection via NFC.

I had the same error, it prompted me to look at the source code and try to fix this.
I refactored several parts of this app (still WIP) and found that it will work when the focusing is set to DMF or MF, also it works in all modes when I added a shutter half-press before trying to take the pictures.
My WIP branch: https://github.com/hameno/timelapse-sony/tree/ilce_7m3

Exact same problem here with RX100VA, the timelapse triggers the AF instead of the shutter unless I'm in MF mode. I could try to build your branch @hameno unless you're going to accept the PR soon and update the play store app @ThibaudM ?
Edit > nvm just saw that you may not accept the PR in #39 for maintainability.