Dropdown Menu button missing

There should be a Dropdown menu on the top of the Lead form to create a new customer,oppertunity or quatation .But it has dissappeared . Please suggest a method to get that again

Version of ERPNext ?
Did you custom the lead form?

Some Screen shots attached ?

Thank you for your quick reply, My ERPNext version is 12.5. I have attached a screenshot.

My ERPNext version is 12.5. I have attached a screenshot.I edited lead using customize

check the web console which will show some error

Oh my bad! The dropdown menu has been disappeared because of an error in my custom script. I found that from the web console as @szufisher suggested and it saved my day. Thank you.