Symptoms

 Attachment field is mark as required in all screen.

Diagnosis

The Attachment field has been marked as Required in the Field Configuration.  By default, Attachment field does not have option to be set as Required. 

Resolution

1. Run the following SQL query to check in which Field Configuration the Attachment field has been marked as Required :

    SELECT fieldlayoutitem.ID, fieldlayout, fieldidentifier, isrequired, name FROM fieldlayoutitem LEFT JOIN fieldlayout ON fieldlayoutitem.fieldlayout = fieldlayout.id WHERE fieldidentifier = 'attachment';

   if the row has isrequired=true , then the field configuration has the Attachment field marked as required

2. backup the JIRA database

3. set the Attachment as Optional by run the SQL update in the JIRA database:

   update fieldlayoutitem set isrequired='false' where fieldidentifier='attachment';

   this query is to update Attachment field as Optional in all Field Configuration

4. restart JIRA