Well, we can't help you unless you use 5.0 or newer. 5.0 is the minimum version we support on the forums. The process on newer revisions of Dolphin is the same, but the GBA <-> GCN connection has always been finicky in Dolphin in new and old versions.
Where exactly does the process fail for you? Does VBA-M just freeze after the BIOS flashes the "Game Boy Advance" logo? Does FSA acknowledge the presence of the emulated GBAs? Not sure, but I believe LLE audio is required for this to work consistently as well; do you have that enabled?
Where exactly does the process fail for you? Does VBA-M just freeze after the BIOS flashes the "Game Boy Advance" logo? Does FSA acknowledge the presence of the emulated GBAs? Not sure, but I believe LLE audio is required for this to work consistently as well; do you have that enabled?