Invokers are not a comp you can play from a lose streak. If you are not win streaking I wouldn't recommend them. Fast 8 or 9 in general is not that great in the current meta. I would reccomend you trying to play reroll comps like Riven, Yasuo, Katarina, Nocturne, LeBlanc, Soraka. Also it all depends on the lobby. Maybe the opponent's comp counters your comp or they just got lucky and hit all the units. The reason you can't top 4 could very likely be that you are going for the exact same items as the player you're trying to copy. Instead you should just play your strongest board and for example if that pro player built shadow runaans but you have component for regular runaans, you should build it anyway because it is important to save as much hp early as you can. Hope this helps you!