I had planted roselle 6 days back in cocopeat sterilised by boiling for 15 minutes then keeping it to cool. The seeds were soaked in water for 3 hours. But so far, none of these have germinated. The seeds are an year old. I have had successful germination two three times back during the last two to three months. I have kept these in shade with indirect sunlight. Temperatures hovering around 23~40 degrees celsius. The trays were first cleaned with detergent then soaked in a solution of Dettol then washed off thoroughly with water.
A quick web search shows that roselle has a germination time of seven to fifteen days. This fits your own observation where a previous batch needed “eight days or so” So after six days, it’s too early to assume that your seeds didn’t germinate.
If you didn’t slightly sand down or nick the seeds to accelerate water hydrating the seed, your germination time will probably be on the longer side anyway.