If the programme has just recently started, you may not see the option to Watch from the Start. This may be because of the scheduled broadcast time. We use the scheduled broadcast time as a reference for when a programme starts. Schedules can and do change, so sometimes it may be slightly off.
Watch from the Start can only rewind up to 2 hours, so if the programme started over 2 hours ago you will not be offered the option to watch from the start. Instead, you will be offered Watch from [two hours ago] - for example, if it’s now 8pm and the programme started at 5pm, you'll be offered Watch from 6pm.