Only those users with the Purchasing or PQuote Approval role will be able to approve PQuotes.

If you want to change this and allow only those users with the role PQuote Approval to approve PQuotes, then you have to find a config variable under ADMIN » Config Settings » Config Settings and give the variable PQuote_Approval_Anyone_If_Under_Value a numeric value.

For any PQuote whose total is above the specified amount, the PQuote Approval role will be required to approve the PQuote. Alternatively, if you want every PQuote to be approved, you can give PQuote_Approval_Anyone_If_Under_Value a very small numeric value such as 0.01 and it will require every PQuote to be approved first in effect.