Problem with 'require_api'

[Syriakes]

Hi,
I have a problem with my mantis.
I have this error when i try to use a plugin 'PHP Fatal error: Uncaught Error: Call to undefined function require_api() in xx/xx/xx/core/access_api.php:42'
Can you know how i can fix it ?
Thank you

[atrol]

Which version of MantisBT are you using?
Which plugin / which version are you trying to use?