YaST2 refuses to mount sda4

I did a fresh install on a SSD hard disk which had a previous installation of opensuse 13.1 with 3 partitions : sda1 was swap; sda2 was / and sda3 was /data from cylinder 3146 until cylinder 15565 (ext4) .
During installation, because of the necessary EFI boot FAT partition i had to repartition the disk in 4 partitions, with sda1 EFI boot 172MB , sda2 swap, sda3 / ending at cylinder 3145 and my sda4 was supposed to be from cylinder 3146 until cylinder 15565 . But it refused to mount because of unknown or non existant file sytem
I forgot about this and thought that i would work after install.
But, after installation the YaST2 partition tool refuses to mount my sda4, though i chose the ext4 option. Again , a message says that it is not allowed to assign a mount point to a device with an unknown or not existant file system .
What can i do to get back my datas previously stored on this supposedly untouched area of the disk ???

It’s a bit hard to know what is happening without more information.

Because your SSD now has an EFI partition, there’s a good chance that it is using a GPT partition table.

One of the features of GPT partitioning, is that there is a backup copy of the partition table near the end of the disk. This may have overwritten part of your “sda4” partition.

Note that I am only guessing here.

What blkid says about this partition?

It is very unclear (at least to me) if you left untouched sda4 and also if the partition table still points to the correct start end end addresses of your former sda4.

Best is of course an

fdisk -l

of the old situation and the same of the new situation.

Thanks to all of you for your quick answers.
I decided to format because it was shorter than hacking all this.
Then i imported the datas from a copy.
Have a good day.

Often the best and easiest (and thus most save) solution when you want to change your partitioning together with an installation.