Uploaded files doesn't work in tasks.

[Артем Киняйкин]

1. I can not attach file in tasks.
Mock-up: 
(translate: failed to load file)

2. I can not download the file from the task.
Mock-up:
 
(translate: failed to save your attachment
Upload the task again, and the try again will add it)

[Angélica Luz]

Hello @Артем Киняйкин,

Welcome to Atlassian Community!

This error is usually related to the size of the file, so it’s important to check: 

Is happening with any type of file that you try to add to any task? 

Is it happening to other users that have the same permissions as you?

Have you checked with your Jira administrator about the size limit of attachments? 

Kind regards,
Angélica