Text equations wil not evaluate

[krissz]

I have equations including text, providing information on source directory & save directors the VBA processes.
In some cells, they evaluate. For example:
In cell B3, ="J:\ACCOUNTS\Credit Cards" & B15 & "" evaluated to J:\ACCOUNTS\Credit Cards\2018\
In cell B4, ="J:\accounts\Xero\Credit Cards" & B15 & "" evaluated to ="J:\accounts\Xero\Credit Cards" & B15 & ""
.
I have tried in B5 =TEXTJOIN(" ",TRUE, "The", "sun", "will", "come", "up", "tomorrow."). This evaluates to 0 (Zero)
All cells are formatted as Text.
.
I also note that if I am copying a cell, the boundary has changed to a coloured box rather the dotted box
I am using Excel 365
.What is happening ?

 

[krissz]

Problem s resolved. I assumed that Excel had become corrupted. Run "Change a Programme" & the matter resolved.
I has re-appeared so something in my VBA code must be going wrong.
Thanks to everybody who read my post