In order for someone to obtain an H4 work permit, one has to actually first pass to H4 status, then file for the EAD or file concurrently for the H4 change of status and the work authorization (EAD). In turn, in order to obtain an H4 status, the spouse of the H4 has to have a valid H1B and meet the requirements to file for the H4 EAD. In case this H1B is not valid or in violation of the H1B rules, the H4 might be terminated and therefore the H4 EAD will not longer be valid.
Since the entire H4 visa and the H4 EAD revolve around the validity of an H1B visa, we highly recommend that the H1B holder make sure that the H1B is being amended accordingly in order that there is no lapse in the H1B status and ultimately affect the H4 visa holders.
Below is a slide on when to file the H1B amendment. Make sure you are checking with your company that they are following the rules on the Matter of Simeio Solutions, LLC. A healthy H1B ultimately means a healthy H4.