The phrase "prove unsatisfactory" is correct and can be used in written English.
It means that something did not meet expectations or failed to meet a desired standard. Example: Despite my initial excitement, the new product proved unsatisfactory when it broke after only one use.
They should turn to these costly drugs only when cheaper alternatives prove unsatisfactory.
This and each subsequent relationship she engineers prove unsatisfactory, chiefly because of her greed and great ambition.
Business for Britain, which wants Britain to exit the EU if reforms prove unsatisfactory, also backs Vote Leave.
During this time, studies have shown that while there are gains to be made, many M.& A. deals prove unsatisfactory for buyers.
If informal means of resolution prove unsatisfactory, the student should set forth in writing a statement of the decision that constitutes the subject matter of the dispute, the grounds on which it is being challenged, and the reasons why the grievant believes that the decision was improperly taken.
The second and third pillars were to be purely "inter-governmental", meaning that everything would be decided consensually no outvoting, no being taken to the European court, no negotiating with the European Parliament.Jacques Delors, the then commission president, predicted at the time that the inter-governmental structure would prove unsatisfactory in practice, and so it has turned out.
At a rehearsal, that recourse proved unsatisfactory as well.
Repeated attempts to fix the deadness of the sound proved unsatisfactory.
If arbitration proves unsatisfactory, Chinese workers or employers can appeal to civil courts.
When further discussions with the hospital proved unsatisfactory, Mr. Zerga contacted the Federal Bureau of Investigation.
When both stories proved unsatisfactory, he combined them in a play.
