Permission to write to external SD card on HTC One M8 running Lollipop
Try applying the SD fix manually, the details are over at XDA. The steps are:


Remount the system partition as read+write (use an app such as ES File Explorer, or enter mount -o remount,rw /system after becoming root in a terminal).
Make a backup of the /system/etc/permissions/platform.xml file, just to be sure.
Look for the XML element android.permission.WRITE_EXTERNAL_STORAGE and make it look like this:

&lt;permission name=android.permission.WRITE_EXTERNAL_STORAGE &gt;
&lt;group gid="sdcard_r" /&gt;
&lt;group gid="sdcard_rw" /&gt;
&lt;group gid="media_rw" /&gt;
&lt;/permission&gt;

Similarly, find the XML element android.permission.WRITE_MEDIA_STORAGE and change it to:

&lt;permission name="android.permission.WRITE_MEDIA_STORAGE" &gt;
&lt;group gid="sdcard_rw" /&gt;
&lt;group gid="media_rw" /&gt;
&lt;/permission&gt;

Set the file permissions to rw-r--r--, either using a file explorer app, or by typing chmod /system/etc/permissions/platform.xml into a root terminal.
Reboot the phone -- this is important for the phone to remount the storage.


All credit goes to poolmaker at XDA.