"Does that normally happen over time? Will it still be effective?"
Tinctures are not stabilized, so the THCA will turn to THC with light, heat, and time. This may cause that skunky odor and taste. Also the terpenes may have evaporated and changed over time. This will cause a much lower efficacy rate, and will now be psychoactive.
If you would like a THCA product that does not turn to THC, check out Better Supplements by Eva https://evaonline.org/collections/all/subscription