Visa update, 10 May 2022:
Tourist e-Visas are now available for 30 days, 1 year or 5 years. For TTC and ATTC: Please apply for the 1-year or 5-year visa. The 30-day visa does not give sufficient time to travel to Rudraprayag, complete the course and depart from India.
Please apply only on this website:
https://indianvisaonline.gov.in/evisa/tvoa.html
Other websites are fraudulent scams that take the payment but do not provide a visa.