Iam a Plat 5 last season and i didnt yest play my placement why im playing with bronze and unranked?

Hey guys Iam a Plat 5 last season and i didnt yet play my placement why im playing with bronze and unranked on normal games ? shouldnt i play with the same tier as me even on normal ? or im mistaken ? And if now why i rarely get a plat or a diamound once and a not so much gold and silver and always like bronze and unranked ? Thanks <3