I've experienced the following problem on Ubuntu GNOME 16.10 and 17.04.
Using Gnome-Network-Manager (I don't want to use other tools) I have issues when I create a wifi hot-spot to allow my Android device to access wired Internet. Sometimes (usually after a fresh boot) the wifi hot-spot works. But after a short while (maybe 10 to 30 minutes), my Android system will disconnect. When I reconnect Android will say something like "Connected, no Internet", but the Internet is available.
This is not a problem with just one Android system or device, I have tested with various versions of Android (Samsung and CynagenMod) and a Mac Book. All with similar issues.
From the Android side it appears that the network signal strengths fluctuates significantly over time.
I have tried various network cards, the internal network card (Intel AC 7260) and a couple of USB network cards. All exhibit similar behavior.
I hope this article can help with your problem.
How to Overcome Ubuntu 17.04 Failed to Make Wifi Hotspot
If Hotspot is on then turn it off first. Go to System Settings > Network
Turn off Hotspot by clicking ON so it becomes OFF
Click Stop Hotspot
Click All Settings > Software and Updates
Make sure the settings shown are checked.
Click the Close button and let Ubuntu 17.04 update after entering the password. Wait for it to finish. Click Reload.
Press Ctrl+Alt+T to start the Terminal application.
Type the following command in Terminal:
Go back to the Network window and click Use as Hotspot then click Turn On.
Hotspot is ON with the name HP-EliteBook-2760p (on my computer)
In order for Android devices to be able to connect to this Hotspot, there is still one more step, namely:
Click Edit Connections
Select Hotspot then click Edit
Change Mode to Hotspot (provided Ad-hoc)
Click Save
Click Enable Wi-Fi to disable your Wi-Fi
Click again Enable Wi-Fi to enable Wi-Fi
And…. Alhamdulillah ... now Hotspot on Ubuntu 17.04 can function normally. Android devices can also connect.