Is it me or my board... Can't catch a cold.

Hi, I'm trying to get back to surfing after being land-locked for 20 years.
I'm 6'2" and 275, (my ideal weight is probably 220-225... But I haven't been that weight since the '90s). I know what to do. Can read the waves, etc, and paddle, but I'm just not catching anything and before I invest in a bigger board, I just wanted to see if maybe i'm delusional about my fitness, or if it really is a board volume issue...
I have a 10'6", 23.25"wide, 3.25 thick, single fin, nose rider... I talked to a couple shapers before I bought this one and basically got "Get the longest, thickest, widest board you can find, and dominate the lineup" talk... Followed by the "...but I know this guy that's 300 pounds, rides a shortboard and rips!"
They were talking about shaping a 10' 24", 4.25 board for me... And I knew about this one and thought, it's pretty close and maybe the difference wouldn't be that bad.
So I took it out on a decent day and it beat the crap out of me. It was unstable... I kept moving around on it, trying to find the balance point but I'm not sure I ever got it. Even though I was at a "learners break" the other newbs were paddling past me like I was standing still. Everything I paddled for went under me, no matter how hard I dug. It wasn't too long before I was wiped and called it a day.
So was it me or the board? Asking for a friend.
I'm 6'2" and 275, (my ideal weight is probably 220-225... But I haven't been that weight since the '90s). I know what to do. Can read the waves, etc, and paddle, but I'm just not catching anything and before I invest in a bigger board, I just wanted to see if maybe i'm delusional about my fitness, or if it really is a board volume issue...
I have a 10'6", 23.25"wide, 3.25 thick, single fin, nose rider... I talked to a couple shapers before I bought this one and basically got "Get the longest, thickest, widest board you can find, and dominate the lineup" talk... Followed by the "...but I know this guy that's 300 pounds, rides a shortboard and rips!"
They were talking about shaping a 10' 24", 4.25 board for me... And I knew about this one and thought, it's pretty close and maybe the difference wouldn't be that bad.
So I took it out on a decent day and it beat the crap out of me. It was unstable... I kept moving around on it, trying to find the balance point but I'm not sure I ever got it. Even though I was at a "learners break" the other newbs were paddling past me like I was standing still. Everything I paddled for went under me, no matter how hard I dug. It wasn't too long before I was wiped and called it a day.
So was it me or the board? Asking for a friend.