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When I try to ad the following, this answer always comes up:oes not work. Same answer: Firefox could not install the file at https://addons.mozilla.org/en-US/firefox/downloads/latest/1865/addon-1865-latest.xpi?src=addondetail because: Unexpected install

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When I try to ad the following the answer is always:

Firefox could not install the file at

https://addons.mozilla.org/en-US/firefox/downloads/latest/1865/addon-1865-latest.xpi?src=addondetail

because: Unexpected installation error Review the Error Console log for more details. -203

This happened

Every time Firefox opened

When I try to ad the following the answer is always: Firefox could not install the file at https://addons.mozilla.org/en-US/firefox/downloads/latest/1865/addon-1865-latest.xpi?src=addondetail because: Unexpected installation error Review the Error Console log for more details. -203 == This happened == Every time Firefox opened

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The answer is in the first thread you started - locking this as a duplicate. https://support.mozilla.com/en-US/forum/1/668996?