Please try the following to see if the issue is resolved.
Steps:
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1.Remaining Space (data)
Check if you have sufficient space left on your Nintendo Switch or smartphone device.
2.Connectivity
Ensure you are playing on a stable connection. Also, try to play using a different source of connectivity, or try to reconnect later at a different time of day to see if there is any difference.
3.Reboot
Reboot your Nintendo Switch or smartphone device and try again.
4. Cache Clear
(Nintendo Switch Version)
From the Pokémon UNITE title screen, press the ZR button and follow the steps to perform a software cache clear.
(Smartphone Version)
From the Pokémon Unite title screen, select the third icon from the top and follow the steps to perform an application cache clear.
5. Device Cache Clear
(Nintendo Switch)
From HOME Menu "Settings" > "System" > "Formatting Options" > "Clear Cache" and select the desired user in order to clear the Nintendo Switch system cache.
*If additional details are required please contact Nintendo Switch support.
*Ensure you do not accidentally delete any Nintendo Switch data.
(Android Device)
From the device "Settings" > "Applications" > "Pokémon Unite" > "Storage" > "Clear Cache"
*Steps may vary depending on device model or operating system. If the steps are unclear please contact customer support for the relevant device platform.
*Ensure you do not accidentally delete any device data.
Please refer to the below article for more information on how to link platforms.
https://app-pu.pokemon-support.com/hc/en-us/articles/4407267006356
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