If you're needing to download any of the National Archives of Ireland's Calendars of grants of probate of wills and letters of administration from 1923 to 1982 (held in CS/HC/PO/4), you're out of luck. This won't be a surprise to some researchers. The online links to download pdf copies of the annual calendars, previously available via the the online catalogue, are out of action.
I don't know how long this has been the case. While an NAI member of staff told me this problem has been ongoing for 'a while', he wasn't able to confirm how long 'a while' meant. However, he was able to tell me that the technical team is aware of the problem and will fix it as soon as is possible.
From 1858 to 1922 (excluding 1921 which has not been digitised), the full collection of calendars cover the whole of the island of Ireland and can be searched at the National Archives of Ireland's Genealogy site. From 1923 to 1982 the NAI's main catalogue cover only the 26 historical counties in the Republic.
(Indexes covering the six counties of Northern Ireland since 1918 are in the Public Record Office of Northern Ireland (PRONI) and are not affected by this NAI techie issue. You can search and view here.)
UPDATE, 26 APRIL 2024: A message advising the above had been placed on the home page of the NAI and a parallel tweet says that researchers can email query@nationalarchives.ie for any calendars they may need.
UPDATE, 20 May 2024: PDFs of the 1923–1982 Calendars are available to download again from the NAI's online catalogue. They have fresh links. Make a simple search using 'Calendar of Wills 19xx', and then download the pdf.