Amasty Resolution Center

Problem with API for Product Attachments

I need your help to send a file by using the API for Product Attchments I saw on the documentation to do a post to /V1/amasty_product_attachment/filemanage/uploadFile. I send this json (I check on google for decode the base 64 and it's work):
  1. {
  2.   "fileContent": {
  3.     "base64_encoded_data": "mybase64pdfstring"
  4.   }
  5. }
and the reponse return : "{"message":"The specified \"%1\" file couldn't be written. %2","parameters":["\/home\/clients\/323374388a426d8af3b8f549d3f05817\/sites\/preprod-oftamedic\/pub\/media\/amasty\/amfile\/tmp\/","Warning!file_put_contents(\/home\/clients\/323374388a426d8af3b8f549d3f05817\/sites\/preprod-oftamedic\/pub\/media\/amasty\/amfile\/tmp\/): failed to open stream: Is a directory"]}". I check the autorisation on folders pub,media,amasty,amfile and tmp and even with 777 that send me this error. Do you have any idea ?

Have a good day

ps : sorry for my english, it's not my native language.