How to delete the DUET ENTERPRISE logo and substitute it

I went to 'Site Settings' > 'Look And Feel' > 'Title, Description and Logo' > 'Insert Logo' > from Computer' pick up a new logo from my computer and clickon 'Ok'.......and I get the message 'Sorry, you don't have access to this page'
I sent a request for access to be granted.
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I went to 'Site Settings' > 'Access Request and Invitation', and saw the pending request I just mentioned. I clicked on 'Permission' and set it to FULL CONTROL and approved it.  I have done it 6 times! and nothing, I can not get the logo
changed and mentioned in the 1st parragraph changed.
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I went to 'Site Settings' > 'Site Permissions' and saw my account Family3Owner has FULL CONTROL. Where else can I go? How can I avoid this problem of 'Sorry, you don't have access to this page'.  Your feedback will be highly appreciated.

Thanks, TempDavid