As you have a new computer and a newly installed FeralHeart, be sure to remember that all presets should be .png files, and you should remember to change that in the preset folder material file as well.
When you export a new preset, you need to do that through the Creative Den on the login screen, and load the 'Preset 3' in Preset Maker. Once the preset has loaded onto your character, you can then export the preset. Do that now, and see if you get a 'Failed to Export' message. If so, continue with the next step.
If your preset has failed to export, you're best off trying to use a different preset folder, mainly because the preset folder you tried to use could be corrupted in some way and does not want to export a preset for you.
If you don't want to do that, then maybe give your preset to someone you can trust and they can export it from the preset folder you're wanting to have used. To do this, follow the following steps:
▸ Give your chosen friend the preset material file and all of the images to go with it (head, body, tail, mane etc).
▸ Once they have placed them in the specific folder you want, get them to launch FeralHeart.
▸ Get them to write your username in the username panel/box on the login screen. Do not give away your password, only the username is needed.
▸ Ask them to go into Preset Maker through the Creative Den and export the preset for you.
Once they go into their 'presets' folder afterwards (Private Presets folder, only if they have preset sync), get them to send you the exported preset so you can place it in your own 'presets' folder, (again, Private Presets folder, only if you have preset sync). Since they entered your username in the username panel on the login screen (hopefully correctly), exporting the preset after automatically exported the preset to your name and it should then work for you just fine once you recieve that. If you're still having issues, then come back and something can be sorted out.