The HENkaku Ensō Custom Firmware has been released a few hours, but it requires your PS Vita device to run a specific firmware, the system software 3.60.
While PS Vitas that are currently running firmware 3.61, 3.63 or 3.65 are totally out of luck, there’s hope for the devices that run a lower firmware.
It is possible to manually update a PS Vita (be it a fat or a slim) to a specific firmware version, if one uses (for example) QCMA as a tool to fool the PS Vita into thinking that the desired firmware is the most recent version (this does not work for downgrades, just saying).
Only a few things are required to update a PS Vita, that is running an older system software, to the desired firmware 3.60. These things are a computer, QCMA and the firmware 3.60 update files. You will need your PS Vita and its USB cable as well.
Simply follow the instructions that are given in the video (linked above), and it should be possible to manually update your PS Vita to firmware 3.60, which in return enables you to use the newly released HENkaku Ensō Custom Firmware. QCMA should be compatible with all older PS Vita firmwares, as long as QCMA’s settings are properly configured.
In case you are using a PS TV (also known as a PS Vita TV), simply drop the firmware updater file (take the PSP2UPDAT.PUP from the 3.60 OFW zip, rename it into PSVUPDAT.PUP and then follow these instructions) onto a regular memory stick, launch your PS TV’s recovery mode and select firmware update via USB device.