Upvote:2
The Answer is not clear.
This TAP page contains this text:
I want to change / cancel my journey:
Change or cancel your trip in advance. Use Manage Booking to change the dates of your flight(s) online and without paying the change fee. One change fee is waived per reservation. Alternatively, you can request the issuance of a voucher for the value of the unused ticket. The voucher will be sent by email and will be valid for a future purchase with TA.
The page says it applies to TAP tickets issued before May 15, 2020. The page also says, however, that this "management plan" "should be in effect until May 11, 2020.
Conclusion: the TAP page does not answer whether a ticket purchased before May 15 may be exchanged for a voucher after May 11.