Impossible to use import PDF

Hello
I tried to use the pdf import and it seems that it doesn’t work properly !
The function generates a loop in my Firefox browser , (latest version: Firefox Quantum 65.0.2(32 bits).)
Now it is impossible to try a new conversion, because , the page "Convert your file"is permanently refreshed and the conversion remains in "Queued" mode.
Maybe the file used, produces the annomaly, during the conversion.
See the attached file .
Many thank's for the solution
Jean-Pierre