Hello. One of the criterias to be eligible for JEE Mains Paper 2 (B.Arch) is that you need to have a minimum of 50% in maths. As mathematics is a compulsory subject for jee mains paper 2 and you have scored less than the required percentage in it so you are not eligible for JEE Mains paper 2 2019.

For more details about eligibility criteria check out the link below.

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-eligibility-criteria/amp

Hope this helps. Good luck!