I don’t think Sonos is going to want to help you out on this. The Sonos app and the speaker firmware must always be up to date on the same version.  Additionally, Sonos regularly updates the cdoe and only supports the most current version of S1 and S2, not any prior versions.  So providing a way to side load the app, and firmware, isn’t going to be sustainable for providing supported updates.  Could be wrong about that though.

Did you get the most current version of the app?

HI, Yes, I downloaded the APK from google playstore, but still no luck on installing it. I can Install the S1 but then it´s requied to upload the app, and since there is no playstore in the tablet, it doesn’t work.

Thanks for the help!

I’m not an expert either, for Android things, but it seems odd to me that you have a version of Android 8.1 which doesn’t have any connection to the Google Store to let you load additional software. 

Have you contacted Philips directly to see why you’re unable to access the store, where you would normally get the software? As @melvimbe states, I’m pretty sure there’s no APK that Sonos provides for install, I’m pretty sure they put the software up just on the various stores. Although I’ve not checked recently, as I recall, even the link they have on their website for their software just take you to the store that’s appropriate for your device. 

if you download it from playstore then there is no chance it not being installing. There might be your mobile memory is full so is not being install. And if you download from 3rd party then this is wrong. 3rd party always hurt your system and your accounts too.