Here r a few more suggestions.
Compare the Marvell wifi driver version of the sp4 that worked with your Verizon Jetpack to the driver version in your sp4.
Verify that you have the latest Marvell driver from Microsoft. If it is the latest try an older version of the driver.
Go to a Verizon store an see if your sp4 works with another Jetpack. If it does work see if there are firmware updates available for the Jetpack or swap yours for another Jetpack.
Try locking your sp4 wifi band to either 2.4 Ghz or 5 Ghz in Device Manager. see below