Versions I always have used were probably signed with Android testkey
However, a few versiosn ago, I found my self needing to sign manually to update. Hard to recall when this started...
Did you once change the signing from testkey or maybe it is a version I got somewhere else caused it ?
Now, to not uninstall and reinstall + download maps again, I am left to manually sign with standard testkey
Note: most releases use the testkey, so not sure what signature you are using by the way
Using testkey ensures compatibility between releasers, even if with TomTom you're the only one left for now :-)
So, here's the apk signed with the classic testkey
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Many thanks for your work