To get Link2SD working I had to format my first partition as FAT (aka Fat16 - NOT Fat32!). The second (for Link2SD afaik) was Ext2. I tried Fat32 but couldn't get that working so stuck with Ext2 for partition 2. I'm using Windows on my main PC so used minitool partition wizard home edition to create the partitions. Minitool is brilliant freeware for Windows, for ages one had to boot linux to fiddle with other than Windoze partitions.
I hope this helps someone else - I was pulling my hair out!! Perhaps a sticky??