Materia and aetherial attributes could not be restored

2 days after melding materia---1st and only meld of one item on 4 different armor pieces---I go to change jobs and the job list states ALL materia is invalid and unrecoverable. this happened to both the gathering and crafting classes. however only the gathering materia is now listed in red while the crafting item still appears as good but the job class is marked just like the gathering and the same message "eqipped, but materia and aetherial attributes could not be restored" . what gives and how is this fixed? and further what could possibly cause this?

"Eqipped, but materia and aetherial attributes could not be restored" is the message you get when the Armoury can only find a piece of equipment in your Chest that matches what you registered, but not the materia it had when you registered it. It'll go ahead and equip it, but you get the message (you get a similar message about how it's a different color if it's dyed differently from what you had registered). If you added materia to the equipment after you registered the gear set, you'll get this message. It'll go away if you just reregister the gear set. As for the stuff in red--some materia will meld but you won't get its full effects (or even any effect) because it's a bad match with the equipment you melded it to. It'll warn you about this when you set up the meld; you may not have noticed that. That's a separate matter from the gear set message.

When you save any gears/accessories set, then change anything within the set such as melding materia or changing colour, that message will appear. You will need to re-save it again.

This message happens between shared gears/accessories. This simply warns you that the original status was altered. Example: if you had some crafting chest piece with some materia on it, but decided to wear a new one and convert the old to materia. This will remind you that the old piece had different status (melded) and now its no longer follows the saved criteria. end.

As for red numbers with melded materia, each item has a cap on the buffs you can add to it and it applies on all gears/accs.

Example if you're melding a Gathering Guerdon Materia I, you'll see on the melding window (Gathering +3), that means full stats are added to the piece.
But if you try a Gathering Guerdon Materia II which should add +4 points to gathering , but you see in the melding window (Gathering +3) in red that means part of materia stats will be lost indicates that max allowed Gathering points can be added is +3 so a Gathering Guerdon Materia I is enough.

Same if you try to meld Vitality materia to any gear that has Vitality in its base, you'll see +0 means it will add nothing. Mind that melding +0 is acceptable if you meld in sake to make Spiritbonding progress faster.