I won my bronze 1 promos, but it did not promote me to silver 5, instead I have to redo my promos

Okay, last night I had 100 lp and was in my promos to get to Silver 5. I won 2, then lost 2. In the final game, I won and afterwards nothing showed up to show that I was promoted to the next tier. I then clicked on my profile and it said I still had 100 lp, and my series had been reset. Has this happened to anyone in the past? If so, is this a glitch, or do you have to win 2 series to get to silver?

Thanks,