Hi and welcome to just answer.
What was the reason for changing the battery?
Thanks for the reply.
It is possible you have a voltage drain and will need further investigation.
Firstly I would like to eliminate the battery as the faulty component .
what you will need to do is make sure the battery is fully charged then disconnect the earth lead over night then reconnect in the morning and try to start.
if it proves ok then we need to test for a voltage drain , would it be possible to obtain an AMP meter for further testing?