Stange Cardinality problem

the steps :

replace empty lines with nothing: replace ' ' by ''.

delete duplicate lines

group them by the number of times a Serial Number appears :

I take only those that will appear once.

I do EXACTLY the same thing for my Dimension Table:

Except that when I import my tables into Power BI and link them in the “Model View” section, Power BI refuses to link the two tables in 1:1 ... even though I have Serial Numbers on both sides:

Inner join. 

All other combinations don't work.

Thank you for your help!

Ps: I've been blocked for two days and I don't understand why it doesn't work
...