Emails only one book and then not another

I am using windows 10 and calibre 5.23

I have this problwm when sharing/emailing a selected book

I select a book
I right click on selected book
I select connect/share from drop down menu
I select email
I select from drop down menu an email listed.

The request is seen moved to jobs in bottom right corner

The job is completed swiftly

When I try to repeat with another book, the new book appears in job [bottom right], It is shown as 'working' unavailable and never completed the job.

This has been a problem for some time.

Please advise

Jerry