tl;dr OnlyOffice Editor is not handling a slightly off-spec .xlsx file in a graceful manner.
Version: ONLYOFFICE Desktop Editors 9.4.0.129 (Linux)
Summary: Opening an .xlsx file and immediately saving it (no edits made) produces a file that displays blank in both MS Excel and LibreOffice Calc, despite the underlying data still being present in the saved file. Two defects were identified in the saved worksheet XML.
Defect 1 — Missing <dimension> element
The original worksheet declares: <dimension ref="A1:AB2501"/>. After the OnlyOffice save, this element is absent entirely from xl/worksheets/sheet1.xml. Readers that rely on <dimension> to determine the sheet’s used range before parsing <sheetData> could treat the sheet as empty. I don’t think this is the actual issue, however.
Defect 2 — Cell type reclassified but value markup not updated
The original file stores literal text cells as (for example): <c r="A1" t="str"><v>DR Name</v></c>. On save, OnlyOffice reclassifies these as t="inlineStr": <c r="A1" t="inlineStr"><v xml:space="preserve">DR Name</v></c>.
This is invalid per the OOXML spec (ECMA-376 / ISO-29500): a cell with t="inlineStr" is required to store its value inside <is><t>...</t></is>, not a bare <v> element. <v> is the correct child for types like str, n, etc., but not inlineStr. The correct output (for the above example) would be: <c r="A1" t="inlineStr"><is><t xml:space="preserve">DR Name</t></is></c>.
This affected all cells in the test file — i.e. every reclassified cell.
Note on the original file: the source t="str" cells with bare <v> are themselves a mild spec deviation (str is meant for cached formula-result strings, not literals) that Excel tolerates leniently. OnlyOffice’s choice to reclassify these as inlineStr on save is arguably the more spec-correct move — but the value markup wasn’t updated to match, producing cells that are invalid under either type’s schema. That mismatch is likely why Excel and LibreOffice fail to display the sheet.
Verification: Manually correcting both issues (re-inserting <dimension>, and rewriting all t="inlineStr"><v>...</v> cells to t="inlineStr"><is><t>...</t></is>) in the saved file’s XML restores correct display in both LibreOffice Calc and Excel, suggesting these two defects can explain the blank-sheet behavior.
Expected behavior: File should open identically after an open-then-save round trip with no user edits.
To Reproduce: Go to this financial site; on the upper-right select Export Options then Full Universe. It’ll take the site ~10 secs to gen a downloadable .xlsx. Using OnlyOffice Desktop Editor, open then save this file. Now open the resulting file in LibreOffice Calc or MS Excel.