Seeking Spell

If you make an attack roll for a spell and miss, you can spend 1 Sorcery Point to reroll the d20, and you must use the new roll.

True Strike

Guided by a flash of magical insight, you make one attack with the weapon used in the spell’s casting. The attack uses your spellcasting ability for the attack and damage rolls instead of using Strength or Dexterity. If the attack deals damage, it can be Radiant damage or the weapon’s normal damage type (your choice).

I've quoted the pertinent rules above. So... True Strike certainly IS a spell. And it certainly does bring about an attack. But the attack is a weapon attack, not a spell attack. Would Seeking Spell be able to be used with it?

Seeking Spell doesn't stipulate "spell attack roll", so I'd say you're good.

Also, there is debate over whether true strike is a weapon attack, spell attack, or both.

Quote from Jurmondur >>

Also, there is debate over whether true strike is a weapon attack, spell attack, or both.

 This is key. You'll have to ask your DM how they want to classify the attack. I play at two different tables, and the DM's went the opposite ways - one said it is a spell attack, the other a weapon attack. The ruling changes what features work with it, so make sure to check with your DM before you commit to using it.

Quote from Jurmondur >>

Also, there is debate over whether true strike is a weapon attack, spell attack, or both.

 Huh, interesting. I suppose that by the literal definitions of those two attacks, it's both.

Spell Attack

A spell attack is an attack roll made as part of a spell or another magical effect. See also chapter 7 (“Casting Spells”).

Weapon Attack

A weapon attack is an attack roll made with a weapon. See also “Weapon.”

It's just that the Attack Roll rule seems to imply it can only be one. I can see why there's debate.

Attack Roll

An attack roll is a D20 Test that represents making an attack with a weapon, an Unarmed Strike, or a spell. See also chapter 1 (“D20 Tests”).

Whether we consider True Strike's attack a weapon attack, a spell attack, or both, I think it would be a really big stretch to say that it doesn't count as "an attack roll for a spell" as described in Seeking Spell. That would be some olympic-level mental gymnastics right there.

Goken Yeah, as Jurmondur said, there's no consensus on the attack type (weapon or spell?), but also about its Range (you, your weapon or a creature?), or how it interacts with features like Agonizing Blast, Potent Cantrip, Potent Spellcasting and the like.

If you're interested in reading others' opinions or joining some of the other threads:

• Is the attack from True Strike both a Weapon and Spell Attack? 
• True Strike Question for the Hive Mind 
• True strike and Arcane Grimoire stack? 

EDIT: just saw wagnarokkr's reply—agreed!