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There is no easy way to hide rows in a sheet in such a way that the user couldn't make them visible simply by removing the filter. The easy way is to hide the entire sheet and extract those dat you want to show into a user form.
In the attached copy of your project I made major organisational changes - just trying to introduce some shape and direction. You may not approve of all of it but that is mutual. I hate the lack of format in your code. You may not care for how hard it is to read your code but I point out that no one wastes more time on reading your code than yourself. The more complicated code you write the greater will be the reward for making it easy to read.
Your code starts with the Workbook_Open event procedure and end with the event procedure for BeforeClose. The Open procedure calls FrmLogin and shuts down the workbook if the user couldn't identify himself. This logic appears unsupported by your code. I have a problem with both the form and the procedure CheckUser. It seems like you intend to create a system of "log in or sign in". Possible, of course, but your design of the Admin sheet seems too complicated and the idea of allowing "Row access" not feasible (see above).
So, in essence I showed how to open and close forms, how to extract a form's result into the main program, and I clarified a lot of the naming. You will find most of your WBSecurity module commented and moved elsewhere, mostly to ThisWorkbook. Code of LoginForm is reorganised and rewritten.
You would now need to clarify the flow of the program: what do you want to do after the password has been accepted? In fact, where is the test that could lead to such acceptance? (Admin!B5:B8 seems superfluous). The logic behind the Register button (label) seems incomplete. Strip the project of everything that is now redundant and, when you come next time, please ask a question :-)