There seem to be differences with the PCs affecting the import and the display.
My home PC imports all files but doesn't display them (blue circle).
My work PC imports some and some not. This depends on the title. Titles with more than one word (so with spaces) aren't imported.
One word titles are imported and interestingly displayed correctly though they include abc2svg syntax.
Not sure what to make out of that, but maybe you do and can test or let me test some more to figure it out.
My theory with the spaces has it's flaws (at least renaming to a one-word title didn't work for Muskrat Ramble)
I include my results and all my abc files I used for the test (again as txt because forum limitations)
results on Surface Book 3 with Microsoft Windows 10 Pro OS 10.0.19045.1
Borneo.abc (with abc2svg syntax) - ignored because of duplicate detection
Borneo Test.abc (same as Borneo.abc but with two words in title) - imported, but blue circle
How Can You Leave Me Now (stripped).abc (stripped to most basic ABC syntax) - imported, but blue circle
How (stripped).abc (same as How Can You Leave Me Now (stripped).abc but with one-word title) - imported, but blue circle
How Can You Leave Me Now.abc (with abc2svg syntax) - imported, but blue circle
How.abc (same as How Can You Leave Me Now.abc but with one-word title) - imported, but blue circle
Muskrat Ramble.abc (with abc2svg syntax) - failed to open and import
Muskrat.abc (same as Muskrat Ramble.abc but with one-word title) - failed to open and import
results on Desktop PC with Microsoft Windows 10 Pro 10.0.19045.1 (home)
Borneo.abc (with abc2svg syntax) - imported, but blue circle
Borneo Test.abc (same as Borneo.abc but with two words in title) - imported, but blue circle
How Can You Leave Me Now (stripped).abc (stripped to most basic ABC syntax) - imported, but blue circle
How (stripped).abc (same as How Can You Leave Me Now (stripped).abc but with one-word title) - imported, but blue circle
How Can You Leave Me Now.abc (with abc2svg syntax) - imported, but blue circle
How.abc (same as How Can You Leave Me Now.abc but with one-word title) - imported, but blue circle
Muskrat Ramble.abc (with abc2svg syntax) - failed to open and import
Muskrat.abc (same as Muskrat Ramble.abc but with one-word title) - failed to open and import
results on HP Pavillion AIO Desktop PC Microsoft Windows 10 Pro 10.0.22631.1 (Win11?)
Borneo.abc (with abc2svg syntax) - imported and displaying with Musescore font which is installed on the system)
Borneo Test.abc (same as Borneo.abc but with two words in title) - imported and displaying, even with Musescore font which is installed on the system)
How Can You Leave Me Now (stripped).abc (stripped to most basic ABC syntax) - imported and displaying normally)
How (stripped).abc (same as How Can You Leave Me Now (stripped).abc but with one-word title) - imported and displaying normally)
How Can You Leave Me Now.abc (with abc2svg syntax) - imported and displaying, even with Musescore font which is installed on the system)
How.abc (same as How Can You Leave Me Now.abc but with one-word title) - imported and displaying, even with Musescore font which is installed on the system)
Muskrat Ramble.abc (with abc2svg syntax) - failed to open and import
Muskrat.abc (same as Muskrat Ramble.abc but with one-word title) - failed to open and import
results on Desktop PC with Microsoft Windows 10 Pro 10.0.19045.1 (work)
Borneo.abc (with abc2svg syntax) - ignored because of duplicate detection
Borneo Test.abc (same as Borneo.abc but with two words in title) - imported and displaying, even with Musescore font which is installed on the system)
How Can You Leave Me Now (stripped).abc (stripped to most basic ABC syntax) - imported and displaying normally)
How (stripped).abc (same as How Can You Leave Me Now (stripped).abc but with one-word title) - imported and displaying normally)
How Can You Leave Me Now.abc (with abc2svg syntax) - ignored because of duplicate detection
How.abc (same as How Can You Leave Me Now.abc but with one-word title)
Muskrat Ramble.abc (with abc2svg syntax) - failed to open and import
Muskrat.abc (same as Muskrat Ramble.abc but with one-word title) - failed to open and import