Looks like they moved to Canton about 1899. The City Directories sometimes reflect the last year's residences, and they are in both Pittsburgh and Canton Directories for 1899:
1899 Canton City Directory
John A [Lola] Fortney, wks J H Eller & Co, res 720 East Fifth
Fortney, Daniel [Sarah], wks J H Eller & Co, res 1003 E Tuscarawas
1902 Canton City Directory
John Fortney not listed
1903 Canton City Directory
John Fortney, teamster, boards 1110 S McKinley Ave
1904
John Fortney not listed
1905
John Fortney, teamster, boards 1110 S McKinley Ave
1906
John Fortney, teamster boards 334 Prospect Ave
1907
John Fortney not listed
Note no mention of Lola after 1902. The directory did include spouses for other men.
Sarah is listed in all those years. She was running a boarding house starting in 1902 so her husband might have died. Others with her at times: Olive, Edna, Richard.
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John returned to Pittsburgh by 1904/5:
1901 Pittsburgh City Directory no John Fortney
1902 no John.
1903 no John.
1905 Pittsburgh City Directory
John A Fortney, manager 510 Market, house at 2711 Webster Ave [assumed Pittsburgh]
1907 no John.
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and he remarrled in Iowa in 1906.