While trying trying to share files from the Mac Air to the Mac Pro, the Mac Air doesn't discover any device

greetings. I bought my Mac Air from Amazon and it's great, I use it to DJ. I'm trying to share files from the Mac Air to the Mac Pro but the Mac Air doesn't discover any device, I was able to share files once but since then it doesn't discover devices. file sharing is turned on on both device. I'm only able to share files from the Mac Pro to The Mac Air at ease but not the other way

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