Method #1 Htc one a9 hard reset
Step 1
Hold down the Power key for a few seconds to switch the gadget off.
Step 2
Press and hold the Volume Down + Power Key at the same time for a few seconds.
Step 3
When you see the three Android pictures, release the held keys.
Step 4
Choose “wipe information/factory reset” from the recovery mode using the Volume button and Power button to confirm.
Step 5
Pick “Yes” to affirm the entire operation. All the data will be reset
Step 6
After that select “reboot system now”.
Method #2 htc a9 hard reset
Step 1
If the screen is off, turn it on.
Step 2
From Main Menu go to Settings and tap Backup and reset.
Step 3
Select Reset phone and select Erase all information.
Step 4
Tap OK to start the entire operation.