In case you don't want to go through the posts, it's not a bug. You need to first get to the six paths rank in one month to be able for you to get the prizes for the rank you'll be in the following month. After reaching six paths the first time, you just need to hit a rank to collect seasonal rewards. For example: reach six paths in one month and the next month, you'll get anbu season rewards if you an anbu. I know it's a dumb rule but this is how it is since other servers have it like this.