Need help with immigration ISA

Hello I'm a french student who juste graduated, I got a job at a japanese company as an engineer with a french program.

I got the job and everything but while applying for my Cerficate of Eligibility I noticed that it is said thrice that only the diploma (here my engineering diploma) is accepted to attest that I'm an engineer. Problem is that due to administrative stuff I will only get the paper in april 2026. I can only get a certificate in the meantime, but as I said it is written 3 times that certificates are not accepted…

With a letter from my school (which is certified by the french government to give diplomas) or a document untitled as Provisional Diploma, will the immigration let me get my CEO? Is immigration comprehensive with these kind of administrative problems? Do I need to contact ISA directly or tell my future company to explain them the situation?

Thanks in advance,

I'm really looking forward to go to Japan and hope this administrative issue won't cause too much trouble…