Data Validation One Dependent

Do you mean you want to use Data Validation to only permit one specific value to be entered?

If so, then in validation criteria choose:
Allow: "List"
Source: enter your permitted value

I have no idea what you're talking about.

Explain your requirement assuming we have no knowledge of your previous threads. Make it completely clear what you are trying to achieve, what you have tried so far, what your problem is, and what your required outcome looks like. Attach a sample workbook if it would help.

Did you resolve your issue?!

If not - forget about 'bothering us', let's get it working. We only have what you type in a thread to work with, though, so you need to make it as clear as you can exactly what your issue is!

I am trying to add a third dependent data validation. Still stuck.

What are you trying to achieve? For dependent validation, you need named ranges which match the values of the 'parent' list.

So, for a validation list to change depending on which product you have chose, you need named ranges "Soft Sphere", "Soft Classic Sphere", "Soft Toric", then the data validation list formula should be, for example:

Formula:

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I've added a couple of examples to your workbook (see attached) - changed cells highlighted yellow, and look at the extra named ranges I have added. You haven't stated any of your actual requirements, so the business logic won't make sense... but you should be able to see how the named ranges need to work, and the data validation references.