Dryer Wont Stay Engaged

Dryer Repair
1

I Have A Koblenz Dryer. Has Worked Fine For 5 Years But Today The Dryer Wont Stay Engaged. If You Hold The Button In It Will Run And Eventually The Gas Flame Will Come On, But If You Release The Button It Quits. Any Suggestions
Thanks

2

Does the drum turn?

3

yes, the drum turns, it works normal except you have to hold the start button down to keep it running