H1 Advise please

I have never travelled before on this visa

My H1 petition is getting expired on 31 July 2019 but my employer is not allowing me to go for stamping as slots are full till July 1st week,Request for your advise

You need the support of your H1B employer for stamping as the H1B was applied by them and they are the ones who need to show that you have a job in US…so, work with them and sort it out.