Link2sd, partition unmounted itself, can't mount back I have Sony Xperia M2 (D2303), and i have had Link2sd for quite some time.
A while back I created a partition in Minitool and mounted it as ext4 in Link2sd. Sometimes it crashed, but usually waiting or restarting would help, because all it needed was to link lib, obb and dex files. However couple days ago i set up Sleep as Android, and before i woke up a family member took the phone for a while (Facebook, Candycrush - which heat up the phone a lot). So when i woke up and tried to shut down the alarm i couldn't, Sleep app kept crashing.
After that I rebooted the phone, only to find out i have 10 installed apps showing, apps showing crash messages, even if i didn't have them in the background. On top of all there is an alarm icon below the clock which i can't turn off because Sleep app is not showing in app drawer.

After 2 days I figured i might flash SuperSu again from twrp, because it wouldn't update binaries.
Tried turning Link2sd into a system app to mount ext4, it only shows some grey screen for a second, nothing changes.
In settings there is Sdcard present with similar space i had before(1 GB more space- probably just app data wiped)
In Link2sd there is Sdcard, as well as the second partition which is showing as unmounted
In DiskInfo app i see partition by its name and allocated size(mmcblk1p2)
I see Sdcard in computer when plugging in usb.
However, I don't see it in Minitool, Disk Management or when running cmd - "diskpart" - "list disk" commands
SDHC card is Kingston 32 GB class 10. Total commander app allows exploring Sdcard which is not appearing in Minitool. Not only is partition missing but Sd card as well.

Thank you.
I dont use Sony Xperia M2 but I had similar problem with Link2SD after upgrade to Android version 6.0.1 on my Samsung NOTE4 N910C.
The reason is - from my point of view - fact, that Link2sd is not longer supported especially for new versions of Android.
I used Apps2SD: All in One Tool[ROOT] (cost aprox 3,5 USD in my Country). Link
-> Look here

Sorry it is in Polish language but of course You can switch to Your language.
This app is still under develop and has more features than Link2SD like working properly recreation of mounting script