I had the same issue, using an original PS Vita Memory card on 3.68.
What I did was the following:
1) Delete tai folder in ux0:
2) Then I navigated to ur0:tai, open the config.txt file and under the “#Henkaku.skprx is hard-coded to load and is not listed here” line you need to insert 1 new line (press triangle, it will give you the option to create a new line)
-On the new line insert “ur0:tai/nonpdrm.skprx” then I created another empty line right below and left it blank, after exiting you will be prompted to save, do so. Then copy the nonpdrm.skprx file in the same folder as where the config.txt file is located.
3) Reboot vita, reinstall Henkaku and try to refresh.