Dassault Systèmes interview questions

had a phone interview with the hiring manager and got called in for onsite interview. HR set up the onsite interview and is smooth. Got interviewed by 4 people, some of them interviewed as a group. lot of technical questions on what i did in my previous projects. this onsite interview went for 4 hours. Worst interview process experience started from this point. HR called me and told that they liked me and they are going to give me an offer and this process took for a week and he even said they are in process releasing an offer for me.. that's it. HR never came back to me with ANY KIND OF UPDATE... After a week, contacted hiring manager and he behaved as if nothing happened so far, no apologies and asked me to come for a second round of interview. I went for 2nd round of onsite interview and spent 3 more hours in their waltham office. Again, that's it.. no reply from HR or hiring manager with any update... very unprofessional and hr & engineering dept don't have any communication