Thank You Page does not load after submission of the registration page

Hi @shreyaaggarwal 
I believe a lot of points are missing in the description to analyze the issue. Can you share a brief of the issue?
Also, there could be a lot of reasons for Thank You not loading. I would suggest trying the below:
- If it's a Marketo LP, check if the Thank You page is approved and you are able to open the URL of the Thank You Page.
- Are there any kind of JS/scripts added on the page? If yes, try to remove them and then check. 
- If that's a follow-up URL, can you check if External URL has been selected in Form Settings and in LP too?
Hope this helps...

Like @awmindtree says, there's not enough (or any!) info here for us to work with.

Please supply a link to your page and fuller description of your observations (i.e. make sure to look for F12 Console errors).