I've tried to install Termux:Api on a rooted Nexus 6P running Nougat (7.1.1 Build NMF26F).
I've tried rebooting and clearing google play cache. To no avail.
Google Play issues the following errorcode -505, which to my understanding is a catch-all for various errors.
The device has sufficient storage memory.
The same happens when trying to install Termux:Task on that device.