I notice that your scripts are missing both compression and filegroup information - just to confirm could you please run the following script and supply us with the output.
And...

message is quite clear - access denied 
the user SQL Server instance is running under needs access to the...

I've seen that happen when there is a tiniest time difference on the clock vs domain server. Setting up a dependency on the time service can solve the issue if...

yeah.. with a totally different error 

Send-MailMessage : The SMTP server requires a secure connection or the client was not authenticated. The server
response was: 5.7.0 Must issue a...

That falls under the category of standards (company) and where none exist personal preference.

On my case standards (and personal preference) are
- tables always aliased
- select, from...

is this what you expect?

if object_id('dbo.ranks') is not null
  drop table dbo.ranks;

create table dbo.ranks
  ( name nvarchar(50) null
  )
  on...

Apologies for my previous post - Missed the fact that the plans were attached.

Agree with Grant - some implicit conversions around suser_name (all but one) but nothing jumping...

ahhhhhh... all queries are based on which user runs it.


uzsakymai.dbo.L0_BP where L0_vart = suser_name()

the above style is all over the place - so...

The sample provided follows standard definition for usage from mainframe style extract files - or PC Cobol files that follow old conventions.
But not just those follow these - I...

pseudo code

read sharepoint list - load onto datatable Invoices

using dbconnection to sqldb -- using transactionscope
{
create temp table (#invoices) -- execute nonquery
...

offcourse not - instead of using my code you reverted back to your original one

$File=gci \\abcd\efgh\ijkl | select -last 1
$Attachment = $File.FullName

you may need to enclose the filename with double quotes on the send mail step

$File="gci \\abcd\efgh\ijkl | select -last 1"
$Attachment = $File

I assume that what you intended here was to get the last file on the folder in question - but...

Assuming your dates always have the _ before them the following will work

declare @t table (a varchar(50))

insert into @t values ('c:\abc_20181008.txt')
insert into...

Seen many developers fall under that trap. Wish that would raise an error.