If your Hotspot is unable to complete challenges on the network, it just may be because of interference or it's position might be poor.
How to Resolve Poor PoC (Proof of Coverage)
Moving the Hotspot to a different window or higher floor if possible.
Metal window screens can also affect RF signals. If those can be removed, it may improve the signal.
Placing the Hotspot outdoors.
Some building materials in the surrounding walls can block RF signals.
For example, Stucco. Buildings that use Stucco have a layer of metal wire. Placing the antenna outdoors would help in this situation. Look for IP-66 Waterproof cases if you will be placing the Hotspot outside. Please see the materials image below.
See if you are in "Relayed" status.
If a Hotspot being relayed, it means it's Internet connection is being relayed through another Hotspot on the Network. To take the Hotspot out of relay requires opening ports on your internet router (to port 44158), and may require some additional work beyond opening ports, like setting a static IP, depending on your router manufacturer. This can help it better maintain sync and properly send/receive transaction receipts for Beacons and Witnesses.
Fully move the antenna outside as high as possible.
If placing the Hotspot near a window does not seem to help, you may proceed to use an external antenna (3DBI, 5.8DBI, 7DBI etc..) and mount it to your roof, or an outside platform.
You can choose to keep the Hotspot indoors by running a LMR-400 cable (Connectors: RP-SMA Male on Hotspot side, and N-Female on the antenna side.
Note, some antennas may have a different connections, such as N-Male, please do your research before purchasing to select the right cables and connections.
Improving Line of Sight
It is important to have line-of-sight between other Hotspots around your area. Ensure you are not blocked by objects or dense trees. A great too to calculate this information is linked below.