I had encountered this issue last week . I have posted the solution here

https://together.jolla.com/question/...post-id-156118


Uninstalled aliendalvik from the Sailfish terminal using the command ' pkcon remove aliendalvik '. (Varoius threads here advise to uninstall the Android Support from the Jolla Store. But in Aquafish, this app is not listed in the store for some reason).

Rebooted the device

From the Sailfish terminal, installed the aliendalvik by issuing the command 'pkcon install aliendalvik' . (I have seen some posts here to do this installation with your WIFI off and Mobile data ON. I installed it while my phone was connected to the WIFI network).

Rebooted the device - all working , whatsapp, skype calls etc all connected with Mobile N/W (3G & 4G).

Hope this helps