Ovulation test- no surge

Sally
TTC conceive again after a miscarriage in July. Started using ovulation tests this month. I'm currently on day 15 of my cycle and no surge has been detected yet! My cycles before the miscarriage were about 32 days and since have been 29-30. When is the best time of day to test? I've been testing first thing in the morning. Apart from yesterday when I tested in the afternoon. Stressing out that maybe I've stopped ovulating altogether.