You are correct Gordl and I suspected this was the cause but like somebody else mentioned, in previous years line 68140 was filled with Box 21 regardless if line 1 was positive or negative. I've checked my past returns and in 2022 I had a negative line 1 in Chart A but line 68140 was filled with the box 21 of the T3. Back then, line 68140 was line 10 of Chart A. Instructions were the same in 2022, do not fill lines 2 to 13 (2 to 19 in 2024) if you have a negative line 1.
So it definitely looks like TurboTax was changed to follow instructions of Chart A but CRA does not accept this. Question remains as to why Turbotax changed this behavior in 2024 ?
