Bleach Major Plot Hole? Spoilers

I don't really remember any fine details, but I would wager its not just "losing your powers" and the specifics of how he lost his powers in both instances.

No, he couldn't just get them back the same way because of how he lost them. First time what he lost was his basic Zanpakuto and couldn't become a shinigami because of that, if I remember correctly and I am going from memory. He regained his powers by awakening his Shikai, so he hadn't lost his powers completely. While loosing them through using Final Getsuga Tenshou erased his shinigami powers. Again I'm going from memory.

Anime Spoiler
The "First time" he lost his power was in the fight vs Reiji & Byakuya where his Zanpakutō broke. (he didnt lost the powers just his Zanpakutō) he fixed that by learning the name of his Zanpakutō and actived the shikai form

The next time he lose his power is in the fight vs Aizen-sama where he had to use Saigo no Getsuga Tenshō which had the drawback to that he loses his shinigami powers (but he had little bit Spiritual Power left inside)

Instead of shinigami powers he learns how to use fullbring from Kūgo who later steals his fullbring power.
After he lost his new fullbring Rukia stabs him with a Sword made out of the Spiritual Power of the Gotei 13´s senior officers to reactive his Spiritual Powers.

Manga Spoiler from the last Arc
next time he loses his power is because Jugram Haschwalth broke Ichigos Bankai Zanpakutō.
He learns from Mayuri that a Broken Bankai cant be fixed. after that the Royal Guard took him to the Soul King Palace in order to reforge his Zanpakutō.

then he got his dual Zanpakutō (which had both of his powers inside | Quincy / Shinigami)

the last time he loses his power in the fight vs Yhwach but Orihime restored his power with her power

i hope its readable xD english is not my native language ^^

I'm pretty sure the first time he lost his powers they were in fact the powers he borrowed from Rukia and when he regained powers they were his own instead of Rukia's, I seem to remember Uruhara saying something along the lines of "you have your own shinigami powers" and Ichigo being suprised when he was helping him regain them.

When he first lost his powers it was because, Byakuya severed the soul chain that Rukia bestowed upon him, the powers he "got back" with Urahara were actually him awakening the Shinigami powers born within him, as explained by Zangetsu. After his bout with Aizen, doing the final Getsuga Tensho severely damaged HIS soul chains which ultimately lead to him slowly losing his powers which is why to get them back the allies of Seiretti pretty much had to omega boost the fuck out of a zanpakuto just to get ichigo to where he was prior the Dangai Transformation. Make sense?