app.xlsm

It is a long set of codes. If you have time, please help look at it.
The error is

Run-time error '91':
Object variable or With block variable not set

When I select Cells A7 and A8,
run Sub Sheet1.t2.
The error will occur.

I have commented where I guess (just I guess) the error comes from
as
when I deleted the code
The error does not come out
but
it cannot function as expected (use the newly opened tab)
My intention was to open a new tab in IE
and
use the new tab

I have worked on it for many hours.
So if you can help test the codes, I would be grateful for your help.
Many thanks in advance.