It took a long time to learn to read errors messages and interpret them for what the actual problem is. Forgetting the semi colon on the end of a class in C++ is another one that will making baffling errors, though I think most modern compilers now say "did you forget a semi colon?"
It takes time to learn all these common simple errors that are impossible to look up in a reference book. (Though now you can usually google them)
I remember getting so frustrated that I couldn't figure out how to cast a function pointer to a C API correctly in C++ correctly that I gave up and switched the entire project to C.
These are the only onse that really stick out in my mind, but there were many more.