This has happened to me for the last few beta releases. It will download the Beta but when it comes to the verifivation step it goes "Verifiying Device" for ages then displays the error message
"Unable to Install Update
An error occured when installing iOS 9.3.3 Public Beta 2.
Retry
Remind Me Later"
I have an iPhone 6. My iOS current version is 9.3.2 (13F68)
I have noicted this hasnt worked for around a month, help!!